I have a .46AX on my PT-40 and I can go straight up indefinitely with it. Not sure what more you would want from a .61.

I made mine with a bolt-on wing. I believe the spars on the PT-40 are spruce, they definitely feel denser and heavier than balsa. The shear webbing is horizontal grain, however... I wish I knew about vertical grain webs when I was building the thing.

James