We certainly need to see more samples.
I think the fact that R437 is C6, and is present in the Iron age, proves that this kind of ancestry was there in Italy since at least the Iron Age. I wonder if this kind of ancestry was more prevalent, than the sample set of Antonio M. et al suggests, during that time. That is the kind of ancestry that ultimately became the majority in the middle ages. Moreover, it was 28% of the Imperial samples in this sample set. I also wonder if other clusters are over represented as well. More studies, with more samples, of this kind will be required to get a better answer.
I think the fact that R1 can be modeled as 35% C6, shows that there may have been admixture between C6 and C7 very early on.