Stock 2t's run an 8.5-1 compression im pretty sure - though i believe the 8 or lower is better ..
A blow thru supercharger - hmms - in all honesty youd probably be better off with a already low comp 2tgeu ( aka tim frosts 4sefed ) and running it via the EFI system , bit i think its got somethign to do with the piston shape and rings to lower it best to create a new thread to get the question asked