I have an Ultra Stick 60 powered by an SK 90. I picked it up literally before the previous owner placed it in the trash. A buddy rebuilt it with lite ply doublers on the outside. Even with an OS .61SF, my original engine until I got the SK, it was nose heavy.

There is a balance point in the manual, 4 1/2", as I recall, but check to be sure. This CG is not tail heavy or sensitive in the least. Build the plane except for the rudder & elevator servos and check the CG. If it is forward of this point, rubber band one servo in the rear and check. I ended up with both servos in the rear with the rudder on top using pull-pull. You cut the hole and put some scrap ply underneath. It's easy, it works like a champ. I have net heard of anyone having a rear mounted servo come out. You will need a couple of 12" extensions.

Don't worry about oil on the servo. I have been using external servos for years and have yet to have a problem.

I know the sides are blue. We didn't have any transparent yellow and this was a trash can plane. But, even at slightly over 8 1/2 lbs it still flies great.