After thinking about it a while, I decided to go ahead and order parts to build a new vertical stabilizer spar. The pieces are relatively cheap and I'll feel better about the airplane. The old spar could probably have been made to work just fine, but I don't want to be lazy and accept work I know isn't as good as it could be.
Also ordered some NAS1097 rivets, which will probably come in handy later on when riveting skins.