Speedpro H405 pistons, what to expect for performance?

I guess they will work fine for just a street car. I guess I had it in my mind that I would at least be in the 9's for compression ratio. I did all the calculations and with my pistons being .040 over it puts me at about 8.7. Anyone know how much the thin head gaskets may bump up the compression?

what is the bore on your engine? and what head gasket did you figure with?