Crashburn, if you are nervous about using your 91 in a 15 pound bird by all means don't, use what you are comfy with and what you think will work for you. I have an APC 14x6 on mine right now and with 15%Cool Power it works great for me. It will loop from level flight but don't expect 100 footers, ain't gonna happen! Like I said, it flies nice and scale and thats what I got that plane for. If I want to rip it up, I also have the GP Gee Bee with a Saito 150 so you see I am a big fan of lots of power too! I wilber, I take no offence to you comments, thats what these forums are for and it is so cool to be able to share thoughts and ideas with people so far away. You obviously know what the left stick is for so you will have no problems at all with your choices. Hopw you guys enjoy your Stearmans as much as I amenjoying mine!!