Frank is correct, a dual-8" diaphragm is more or less equivalent to a single-10.75" booster in terms of gain, albeit slightly more on paper. The dual-9" booster like those used on the C5 Corvettes provides approximately 30% more boost than the single-10.75", so either should be step in the right direction without any real drawbacks to speak of.
Tobin
KORE3