I fly my shoestring with the OS61fx and a 13x6 APC. I get 10600 rpm. Using bisson pitts muffler.

Flies great, very light plane, vertical good but not unlimited.

Make sure prop is nicely sanded and balanced, and engine is properly broken in.

Used to use top flite wooden 13x6's but on the grass runways it is hard to avoid a few nose-overs with this airplane. after a few busted wooden props i switched to the APC's and liked them better.

crashed it on an 'impatient landing approach' at end of the fall and broke the fuselage completely in half. wing broke off, one wingtip shattered and then the other.

rebuilt it this winter and eager to see how she flies with a little extra weight, but should be a bit stronger now too.

i like the look of the wheel pants and will probably put them back on after a few flights.

attached pic is as she looks after rebuild.