Definitely change the horizontal stab. I built one up from balsa using enlarged Brian Taylor plans for my Yellow. Much lighter, not nearly as wavy, and easier to put the scale hinge line on a built up one. Also, the plywood cores used for the rudder and elevators should either be drilled full of holes or, better yet, throw them away and make them out of something lighter. Spits are notoriously tail heavy! Good luck with it!