Wiseco has .010" over pistons which equate to Stock 10:1 Compression for XB9 or 12:1 Compression for XB12
NHRS has .015" over pistons for XB9 with 10.5:1 Compression
If you are putting a Buell XB9 topend on your S1...you need to be aware the head chamber is different on all 04+ XL and 03-10 XB's and the cylinders have bigger fins for better heat dissipation...ALSO putting 12:1 compression to a stock 1200cc crank shaft will guarantee a short life span...either bent rods, crank bearing or rod bearing failure. if you are going to put that much compression to it...you better have a crank built to handle it.