Rossis can certainly scream, but run well at much lower RPM, too. Plus, Rossi made 'longstroke' versions of their engines, too. Chip Hyde ran a Rossi (FIRE) in his Hanson Dalotel with a 12x9 prop. The engine ran great and Chip flew it very well; much closer to constant speed desired today than some of other designs at the time (EG. Atlanta, Aurora). Pattern fliers during the 'transition period' (from open to aresti aerobatics) found overall performance improved with better prop choices (12x8 vs 11x7, for example) even on the 'classic' BPA designs.
-Will B.