U CAN DO .60, OS .91FS. Fun plane! Actually the first time I pulled it off was an accident, I gave too much opposite rudder and next thing I knew I had done it! Only about 15' in diameter but it was a KNE none the less. So I tried it again a few more times and it seemed pretty easy to just give enough rudder to make the loop and just balance with the ailerons. The harderst part is the last 1/4 of the loop. Working throttle, rudder and ailerons all at once while overcoming the B-Hole pucker factor and the urge to bail out is a lot to manage at once. I tried bigger loops but they are much more difficult to manage in the last 1/4 have to really focus, I havent quite been able to cleanly get around without rolling over to inverted and wobbling around right at the end of it. I think the key is to have your plane trimmed so that all you need for a straight knife edge is rudder, if my plane didnt go in a straight line it wouldnt work for me. ALso Im trying this about 150' off the ground.. Ive only been RC flying since September but man I am hooked!! What a fun hobby..