Thunder Tiger 61 GP engine for fun fly plane.
I think there are some guys up north part of US the takes a morris knife, and makes it into a 60size.
Here is from what I remember, extend the wing by 1 bay on each side. then extend fuselageat the tail by either 4" or 6" They were running OS61FX on theirs. I think the weight was around 5.75lbs.
Do a search on Knifes here in the funfly column ifyour interested.