As you pointed out , CR wants to be around 10.5;1 & above with alu heads , anything much less will soot & can be a PITA to tune , more power will be had increasing CR from 9.9 to 10.5 than from 10.5 to 11.1 all being relative........cutting the heads .040" should net around 78cc bringing SCR up to around 10.5/1 , piston to valve should be around .080" , may not need to cut those pistons.