I have a modified Alpha .455 in my Cermark Bobcat...(it has the sleeve mods as per the 2 stroke mods thread )

W/ an APC 10 X 7 and Tower muffler it will turn 13,500 on 10% and over 14,000 w/ an APC 12 X 4 FWIW

I took the flywheel off too...

edit: I had to put bearings in it fairly early in it's life as it was in our club trainer and suffered some abuse...( little or no ARO and un-balanced props due to many ground strikes )