How much HP does the head shim rob?

[Viper190MCX]

A .066" head shim costs about 5-6 hp compared to stock compression, same way with your retarded timing (so about 10-12 hp total over a stock compression, stocking timing motor). You'd need almost 2 lbs more boost on the supercharger to make the same horsepower as previously. Now the nice thing is, even with the compression lowered, timing reduced, etc you could damn near run 87 octane with 6.5 lbs of boost. 8.5 lbs of boost is still safe on 91 octane fuel with that setup, I've had plenty of guys run 10 lbs of boost, maybe a little on the edge, you have to decide where you're happy at.

Hi Ulmer
I have a 16 viper with carrillo low comp piston 9.5-1 and a 0.047" (1.2mm) head shim.
What do you think the CR is with this setup, and how many hp loss compared stock compression??