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Its simply an issue of preignition. Flatheads are much more prone to knocking and if you start with relatively high compression it will knock like crazy when the boost kicks in. I don't know who you can ask about a suitable compression ratio for the boost you are planning. The flathead Ford people are sure to have an opinion, or Jack Vines may have some experience.
Key to controlling knock in flatheads is maintaining minimum squish/quench across as much of the piston surface as possible.
That's why it's good science to square the block deck, measure carefully, order your forged pistons with a high ring placement and to ride at zero deck. By closing the quench area to just the thickness of the gasket, this forces the air/fuel mixture into the recess in the head. The smaller the area, the less likely it is to knock.
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Usually engines with turbos or superchargers will have lower static compression ratios because it allows you to fill more combustion chamber with the air/fuel mixture that you are cramming in with your turbo or supercharger.
For true, usually. However, Paxtons were designed for small engines turning higher RPM; on a 327" displacement, at no more than 4,000 RPM, it's unlikely a Paxton will show more than 3-4# boost.
Yes, a Paxton can be overdriven with a larger crank pulley and thus make more boost at a lower engine RPM, but the ball drive life becomes measured in hours.
jack vines
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