ORIGINAL: daven
I'm using an O.S . 91 fx two stroke in mine, and the balance comes out perfect. I would stick with a heavier model and keep the balanced towards the nose.
A .91 fx that thing must be a rocket!!! I am using a 52 4 stroke in mine and it flys fine but not fast and no power for reserve. I had to add a 2oz prop nut and 14 grms of lead at the firewall to balance so I figure I have some room for a larger motor... I just want to keep this bird as light as possible. I am searching for a different motor for mine... I like the 4 strokes. I have a 61 tt pro in the basement I had in a Shoestring. I have a .91 fx too in a stuka. Seems like over kill for a little plane... WOW>. Love to see that rocket.