I think you are on the right path here, but... You should not use only Croats (Croatia) in your analysis, but try to look at the Balkans as a whole. And on the map bellow you will see the pattern you are looking for. The previous native population retreated to those areas where E-V13 has a higher frequency.
Looking at R1a:Slavs as 1:1 connection is a trick. It messed up the minds of many people.
You can see exactly which haplogroups were there before the Slavs and which ones came with the Slavs from this data. They created this study with the goal to prove paleolithic continuity of Haplogroup I in Croatia, but given we our current knowledge of the unlikeliness of paleolithic continuity all it does is show us which haplogroups were pre Slav.
Every Haplogroup that has a Higher frequency for "Croation mainlaind" than for "Brac-Hvar-Korkula" is Slav, every Haplogroup that has a Higher frequency for "Brac-Hvar-Korkula" than for "Croatian Mainland" is Pre-Slav.
Slav:
R1a-SRY
R1b-M173
Pre-Slav:
I-M170
G-M201
P*
J
The G/P*/J aren't really of any value because it is based off of <10 results. I think this study is only significant for I, R1a, and R1b.
[TABLE="class: cms_table_data"]
[TR]
[TH="class: cms_table_last cms_table_rowsep"][/TH]
[TH="class: cms_table_last cms_table_rowsep, align: center"]
Frequency[/TH]
[TH="class: cms_table_last cms_table_rowsep, align: center"]
No[/TH]
[TH="class: cms_table_last cms_table_rowsep, align: center"]
95% CR[/TH]
[/TR]
[TR="class: cms_table_odd"]
[TD]
I-M170[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD]Croatian mainland[/TD]
[TD]0.376[/TD]
[TD]41[/TD]
[TD]0.291–0.470[/TD]
[/TR]
[TR="class: cms_table_odd"]
[TD]Krk[/TD]
[TD]0.284[/TD]
[TD]21[/TD]
[TD]0.194–0.396[/TD]
[/TR]
[TR]
[TD]Bra
[/TD]
[TD]0.551[/TD]
[TD]27[/TD]
[TD]0.413–0.682[/TD]
[/TR]
[TR="class: cms_table_odd"]
[TD]Hvar[/TD]
[TD]0.659[/TD]
[TD]60[/TD]
[TD]0.557–0.749[/TD]
[/TR]
[TR]
[TD]Kor
ula[/TD]
[TD]0.537[/TD]
[TD]72[/TD]
[TD]0.453–0.620[/TD]
[/TR]
[TR="class: cms_table_odd"]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD]
G-M201[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR="class: cms_table_odd"]
[TD]Croatian mainland[/TD]
[TD]0.009[/TD]
[TD]1[/TD]
[TD]0.002–0.050[/TD]
[/TR]
[TR]
[TD]Krk[/TD]
[TD]0.000[/TD]
[TD]0[/TD]
[TD]0[/TD]
[/TR]
[TR="class: cms_table_odd"]
[TD]Bra
[/TD]
[TD]0.061[/TD]
[TD]3[/TD]
[TD]0.022–0.165[/TD]
[/TR]
[TR]
[TD]Hvar[/TD]
[TD]0.011[/TD]
[TD]1[/TD]
[TD]0.003–0.058[/TD]
[/TR]
[TR="class: cms_table_odd"]
[TD]Kor
ula[/TD]
[TD]0.104[/TD]
[TD]14[/TD]
[TD]0.064–0.168[/TD]
[/TR]
[TR]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR="class: cms_table_odd"]
[TD]
F-M89[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD]Croatian mainland[/TD]
[TD]0.018[/TD]
[TD]2[/TD]
[TD]0.006–0.064[/TD]
[/TR]
[TR="class: cms_table_odd"]
[TD]Krk[/TD]
[TD]0.000[/TD]
[TD]0[/TD]
[TD]0[/TD]
[/TR]
[TR]
[TD]Bra
[/TD]
[TD]0.020[/TD]
[TD]1[/TD]
[TD]0.005–0.106[/TD]
[/TR]
[TR="class: cms_table_odd"]
[TD]Hvar[/TD]
[TD]0.011[/TD]
[TD]1[/TD]
[TD]0.003–0.058[/TD]
[/TR]
[TR]
[TD]Kor
ula[/TD]
[TD]0.015[/TD]
[TD]2[/TD]
[TD]0.005–0.052[/TD]
[/TR]
[TR="class: cms_table_odd"]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD]
R1a-SRY[SUB]10831[/SUB][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR="class: cms_table_odd"]
[TD]Croatian mainland[/TD]
[TD]0.339[/TD]
[TD]37[/TD]
[TD]0.257–0.433[/TD]
[/TR]
[TR]
[TD]Krk[/TD]
[TD]0.378[/TD]
[TD]28[/TD]
[TD]0.276–0.493[/TD]
[/TR]
[TR="class: cms_table_odd"]
[TD]Bra
[/TD]
[TD]0.265[/TD]
[TD]13[/TD]
[TD]0.162–0.403[/TD]
[/TR]
[TR]
[TD]Hvar[/TD]
[TD]0.087[/TD]
[TD]8[/TD]
[TD]0.045–0.162[/TD]
[/TR]
[TR="class: cms_table_odd"]
[TD]Kor
ula[/TD]
[TD]0.201[/TD]
[TD]27[/TD]
[TD]0.142–0.0277[/TD]
[/TR]
[TR]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR="class: cms_table_odd"]
[TD]
R1b-M173[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD]Croatian mainland[/TD]
[TD]0.156[/TD]
[TD]17[/TD]
[TD]0.100–0.236[/TD]
[/TR]
[TR="class: cms_table_odd"]
[TD]Krk[/TD]
[TD]0.162[/TD]
[TD]12[/TD]
[TD]0.096–0.263[/TD]
[/TR]
[TR]
[TD]Bra
[/TD]
[TD]0.061[/TD]
[TD]3[/TD]
[TD]0.022–0.165[/TD]
[/TR]
[TR="class: cms_table_odd"]
[TD]Hvar[/TD]
[TD]0.011[/TD]
[TD]1[/TD]
[TD]0.003–0.059[/TD]
[/TR]
[TR]
[TD]Kor
ula[/TD]
[TD]0.015[/TD]
[TD]1[/TD]
[TD]0.005–0.052[/TD]
[/TR]
[TR="class: cms_table_odd"]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD]
P*-92R7[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR="class: cms_table_odd"]
[TD]Croatian mainland[/TD]
[TD]0.018[/TD]
[TD]2[/TD]
[TD]0.006–0.064[/TD]
[/TR]
[TR]
[TD]Krk[/TD]
[TD]0.000[/TD]
[TD]0[/TD]
[TD]0[/TD]
[/TR]
[TR="class: cms_table_odd"]
[TD]Bra
[/TD]
[TD]0.000[/TD]
[TD]0[/TD]
[TD]0[/TD]
[/TR]
[TR]
[TD]Hvar[/TD]
[TD]0.140[/TD]
[TD]13[/TD]
[TD]0.085–0.227[/TD]
[/TR]
[TR="class: cms_table_odd"]
[TD]Kor
ula[/TD]
[TD]0.060[/TD]
[TD]8[/TD]
[TD]0.026–0.104[/TD]
[/TR]
[TR]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR="class: cms_table_odd"]
[TD]
E-SRY[SUB]4064[/SUB][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD]Croatian mainland[/TD]
[TD]0.055[/TD]
[TD]6[/TD]
[TD]0.026–0.115[/TD]
[/TR]
[TR="class: cms_table_odd"]
[TD]Krk[/TD]
[TD]0.068[/TD]
[TD]5[/TD]
[TD]0.030–0.149[/TD]
[/TR]
[TR]
[TD]Bra
[/TD]
[TD]0.041[/TD]
[TD]2[/TD]
[TD]0.013–0.137[/TD]
[/TR]
[TR="class: cms_table_odd"]
[TD]Hvar[/TD]
[TD]0.043[/TD]
[TD]4[/TD]
[TD]0.018–0.106[/TD]
[/TR]
[TR]
[TD]Kor
ula[/TD]
[TD]0.037[/TD]
[TD]5[/TD]
[TD]0.016–0.084[/TD]
[/TR]
[TR="class: cms_table_odd"]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD]
J-12f2[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR="class: cms_table_odd"]
[TD]Croatian mainland[/TD]
[TD]0.018[/TD]
[TD]2[/TD]
[TD]0.006–0.064[/TD]
[/TR]
[TR]
[TD]Krk[/TD]
[TD]0.108[/TD]
[TD]8[/TD]
[TD]0.056–0.199[/TD]
[/TR]
[TR="class: cms_table_odd"]
[TD]Bra
[/TD]
[TD]0.000[/TD]
[TD]0[/TD]
[TD]0[/TD]
[/TR]
[TR]
[TD]Hvar[/TD]
[TD]0.033[/TD]
[TD]3[/TD]
[TD]0.012–0.091[/TD]
[/TR]
[TR="class: cms_table_odd"]
[TD]Kor
ula[/TD]
[TD]0.022[/TD]
[TD]3[/TD]
[TD]0.008–0.064[/TD]
[/TR]
[TR]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR="class: cms_table_odd"]
[TD]
K-M9[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD]Croatian mainland[/TD]
[TD]0.009[/TD]
[TD]1[/TD]
[TD]0.002–0.050[/TD]
[/TR]
[TR="class: cms_table_odd"]
[TD]Krk[/TD]
[TD]0.000[/TD]
[TD]0[/TD]
[TD]0[/TD]
[/TR]
[TR]
[TD]Bra
[/TD]
[TD]0.000[/TD]
[TD]0[/TD]
[TD]0[/TD]
[/TR]
[TR="class: cms_table_odd"]
[TD]Hvar[/TD]
[TD]0.000[/TD]
[TD]0[/TD]
[TD]0[/TD]
[/TR]
[TR]
[TD="class: cms_table_last"]Kor
ula[/TD]
[TD="class: cms_table_last"]0.015[/TD]
[TD="class: cms_table_last"]2[/TD]
[TD="class: cms_table_last"]0.005–0.052[/TD]
[/TR]
[/TABLE]