I've built three 4*40's. THe first had the Sullivan unit, the second 2 used the stock tailwheel assembly per instructions.

The sullivan is a very nice assembly, I used it in my first 4*40. Be aware that it will add weight that you'll have to counterbalance in the engine compartment. If you do use it, use a very stiff spring or solid wire into the rudder. In a cross wind, the springs aren't enough to overcome the side loads of the wind while you taxi out. That's just something to be aware of.

The 2nd and 3rd built with the stock tailwheel assembly. No problems at all. The tail isn't on the ground all that long anyway to let vibration or steering be a problem for the hinges. My 2nd and 3rd are still flying just fine.

You might want to beef up where the stringers meet the former behind the 'headrest'. That's a weak area, though easily fixed if you have a hard landing. Also, use some pine or other hardwood to beef up the threaded blocks where the wing bolts into the fuse. The balsa blocks in there just aren't strong enough...

You're going to love this plane.

Just my $.02

Bob