im running 8.5:1. BUT there are great upsides to higher, for get the tune. guys have that mastered. especially with a huge intercooler/and meth.
from where i sit. fuel is the big issue for turbo. BSFC's worse than .55 are common. you run a higher CR and sequeeze a LOT more out of the available fuel you wont join me and others who have to throw a freakin ton at it.
the other side of it is: if i upgrade the fuel theres a much higher limit for boost, and it will make up for the lower compression at some point.
96 mustang GT-93 teksid 4v forged: ported heads, kellogg crank, billet i-beams, CP forged pistons, 9.4:1, BIG turbo, 4x28x12 fmic, big boost.
2011 GT 300A, 3.73, M6, spoiler delete, brembos