a 72cc head will drop the compression but u know for sure that you have 9.5 compression???
So u just look at the 9.5 compression if thats what its been tested to be.

weiand... not familar with there stuff... but i think thats the roots style blower right?

well 6 lbs is usually fairly safe on a stock LT1 10.5:1 or LS1 motor at 10.2:1 .... Some argue you can get more like 9 safely but i dont have enough experience on them... just what i read on cz28.com and most would say 9 is too much unless u know what your doing.
So your at 9.5 on a forged engine.. I'd think 9 lbs would be no problem... I would even say 12 would be no problem with an intercooler.

Course I'd do more reseach into it.