Triangle balsa stock is a good idea. When I built the Sig LT40 I heeded the recommendation in the instructions too add on the tail where the horizontal and vertical stabs meet. When you trim back the covering, look carefully for any fuel oil contamination that may seeped into the wood. Back in the old days the fix for this was good old K2R Spot lifter, which would draw out the oil onto the surface powder. I haven`t had to perform this chore in a long time and don`t know if you can even get the stuff any more. Hopefully all your wood is nice and dry.