I've built the WB 40 and have seen the WB 60 kit. I think the the Epsilon is even better in terms of quality and the way they designed it to build. My Epsilon kit seemed the best of all 3 kits. A lot of the build, such as wings/stab/rudder is the same as the others, but the fuselage seems to be better thought out. The only thing that I don't like is the heavy dural split main gear. The stock is too think and heavy for me and I may look for another gear to use. The plans call for the split gear to mount inside of the fuselage but I'll mount mine on the bottom instead.