First I`m thinking a 91 FX is a bit small for the cando 60 which really is a big bird.
My 91 FX turns APC 14-6 at 11500 rpm and MAS Scimitar 14-6 at 12500 rpm and it pulls REAL hard. APC 13-6 spins 12800 rpm and feels to small. It is now mounted in a Katana 70 profile and fitted with a wood 15-6 to hover at less rpm with less noise. The ting is that the stock muffler really kills the engine. To get more power from your 91 FX remove the baffle inside the muffler and drill the outlet stinger of the muffler to the max, this will wake up the engine quite a bit and noise will still be bearable. I used this configuration for a while and then bought a Tower .75 muffler for 18$. That muffler is 2 oz lighter in weight and releases even more power. My tach reading of the APC 14-6 and APC 13-6 with Tower muffler is actually on par or a little ahead of what the the very expensive jettstream muffler will provide. Check the diagram halfway down this site: http://www.jettengineering.com/

The direct link didn`t work. Just click the "muffler and accessories" to the left and then the "Turbo-Jett In-Cowl Mufflers" second from the top page, and then the diagram will appear about halfway down the page. There`s a comparison between the stock muffler, Jettstream muffler and the Turbo-Jett In-Cowl Muffler fitted on the 91 FX

If you are not happy then wake up that engine instead of fitting a toothpick propeller