I'm running a Polka Pickle with the (small), 8cm hot side. For those unfamiliar, that is a Blouch 2.5XTR, a stock location ball bearing turbo with internal wastegate. It has worked really well for me, in combo with my mild porting, Full Race pipes and my other mods. At EFI, on their Mustang dyno, the late Chris S. tuned me to a mild, road racing 395WHP/393FPT.What turbo are you running scargo? That's sort of why I didn't say ring gap numbers before. For top rings stock says .008 - .010. CP is around .020. Cosworth is .012 - .018. They're so all over the place that my numbers don't mean much. Plus it depends on the ring material, and use of the car. For my personal car if it ever manages to get finished I'm going to run .015. That is likely to be on a pump gas 35r setup. I am almost finished with another engine I did .015 top gap on, it was with Manley pistons. Should be around 350 whp or so when it's done. If it butts rings then I have an expensive repair bill for someone and I'll post on here not to do it lol. But it shouldn't. I don't like running huge gaps because for one I can't see the rings getting so much hotter that they need to be double the factory clearance and for two I think it's why it seems like an accepted fact that built motors don't last like a stock one in terms of mileage.
I am not sure why stock gap would be so small, but it could be the cast pistons playing a part. I don't want to run excessive gap either, but I don't want to go against CP specs either.
My younger brother was a turbo'd VW drag guy and he liked Total Seal gapless rings. I see they do not recommend their rings for turbo applications. Not sure why... A lot will depend on the boost you wish to run. YMMV I am still learning...