Again guys, new here, so if this topic is old news, forgive me. After I get through being nostalgic and get that Vigilante done, the Seahawk is my next most wanted to build rocket. Thoughts? suggestions? The upper section is BT-55, but what is the lower section? It is 1.75", but what tube size is that? The original BTs were slotted for the plastic fins. Am I wrong that I am going to have to fudge with regular balsa and just do the best I can with the lower fins (seems those original lower fins were knife sharp). Any input is appreciated. Thanks.