That's what I was going to do, only instead of leaving the back open cover it with some thin aluminum sheeting or something. I at least figured it would help keep dirt out of the hole in the back. Did you grind down all the stuff that's in the back? Yours is really clean, you can see in the pics of mine that there are alot of places where screws used to go that stick out considerably.

Also, I can't tell from the picture: did you plug the hole or did you simply cut the crank outside of the seal? I think I'm just going to cut my crank outside the oil seal and call it done. If I ever get a leak I'll simply grind it down and plug it but until then that should be good enough.

Are you running yours on gas/glow mix? I'm trying to figure out whether or not I need to switch from the 8mm venturi to the 11mm, or whether I can simply drill out the one I have.