With the 78cc chamber of the TF head, Cometic .045 head gasket, and -.003 deck clearance it calculated out to somewhere between 12.3 and 12.4 : 1. I had the pistons lightened and that shaved off about 40 grams and I want to say they ended up weighing around 580 grams when finished. I think the Performer head may have a slightly smaller (75cc?) chamber? To get to 10.5 : 1 you will probably still need a small dome. You may be able to achieve that CR by shaving the heads and running a thinner head gasket although just having a custom piston made may be simpler and less expensive. To be honest these pistons I had made were fully custom down to the shape of the dome based on the TF head and only cost a few hundred dollars more than the 383 w/440 rod pistons Diamond lists part numbers for. The worst part for me was trying to find a set of Molnar or K1 rods with the supply chain issues but after posting a want ad here I was lucky enough to have a member here contact me and he was nice enough to sell me a set he wasn't using.