It depends on flame speed, with a much shorter stroke the pistons are actually moving slower MPH up and down thus you can run a higher RPM and not outrun the flame front. Like was mentioned motorcycle engines routinely turn 12-15,000 RPM on pump gas butt they are very small displacement but the flame speed and piston speed are probably similar to a stroker engine. A piston going 12,000 RPM with a 2 inch stroke is not traveling any faster on average than a piston in a 4 inch stroke engine running 6000 RPM.

I think what your considering is actually going to be tough because you need a big dome for a hemi to have much compression already, to get a small cube engine to have a lot of compression with those ginormous chambers you are going to need a massive dome that will make a heavy piston and take much longer for the flame front to work it's way around and that is not RPM friendly. Maybe you could weld up the sides of the chamber some like a GEN III hemi so you don't need as big of a dome. You will also still have things like pushrod weight limiting what you can do with the valve train.

Sounds like a fun project, I just don't think the pump gas is going to be a limiting factor.