So, untapered fins it is; I started on the Excelsior Honest Goon.
What Excelsior sells is the decals and a page of instructions. The “traditional” way to build a goony, and what the instructions tell you, is to bash an Estes Baby Bertha kit. Typically you’d use everything from the kit but the fins, which you’d replace with ones specific to the goony design. But in the case of the Honest Goon, you’re also not using the Baby Bertha nose cone. I had everything else in my parts stash — BT-60, BT-20, hook, thrust ring, launch lug — except I was out of BT-20 to BT-60 centering rings. So I bought some of those from JonRocket.com and was set to go.
I’d already bought the parts for the nose section — from Semroc, back in 2013. A BNC 70AJ nose cone, a TA-6070 transition, and some BT-70 tubing from which I cut a 7/8″ slice. There was way too much shoulder for that little length of tube, so the excess needed to be sawed off. Then the three pieces go together to form the nose section. I haven’t glued it yet, just dry fit.