On an earlier thread you mentioned using 64cc heads,5.7 rods, with a 5cc flat top piston, and I said it would give you over 11:1 CR.
The kit your refering to now(1-40805-1) has 6" rods and pistons with a dish/2 valve reliefs and specs at 19.6cc volume. I come up with a CR of 9.03:1 if the piston is .025" in the hole with a 64cc head. I get 8.5:1 CR if I switch to 70cc head.
If you haven't got either one yet(heads or rotating assy) you might want to look at a kit 1-40755B1(2 piece RMS,forged crank, the good 6" rods w/7/16" bolts, forged pistons w/5cc flat tops. bearings, and internally balanced from SCAT) and buy heads with 70cc chamber to get 9.8:1 CR with .040" gasket and pistons .025" in the hole. Pretty much what I'm doingexcept I had to bore out to .040" over instead of 4.030". Kit 1-40755-1 comes without bearings and is unbalanced. Just a thought.