opinions welcome on build.

no but i have number of friends that do, and they make big numbers. Quick is a relative term.
Compare a 4" stroke to a 3.5" stroke.In one crankshaft revolution the 3.5" stroke piston travels
14 " while the 4" stroke travels 16"..or 2 inches more. Now multiply that by 6000 rpm.
..each 4" stroke piston will have to travel 1000 ft. further (12000 inches) than the 3.5"
in same amount of time.