Mmm... Normally you would not need to lower compression when using low pressure supercharger. I remember about this long time ago about those supercharged and turbocharged 535i... can't remember who did it... famous company.
To lower compression ratio, you would need shorter connecting rod or a different crankshaft. However, to do high pressure supercharging or turbocharging, you need stronger crankshaft, connecting rod, and piston. This gets into $$$$. JustinRed5 would have alot more experience in this matter.