I rounded the leading edges on the fins, then papered them. My usual, good old printer paper and glue stick. Here they are: um, under that board. I don’t know if it actually helps to weight them while the glue cures, but I do it anyway. I don’t think it hurts.
Pro tip: Make sure the thrust rings are at the same ends of the tubes before gluing. In fact it probably would have been a better idea to do the thrust rings after gluing the tubes together, just to be sure. You know, like it says in the Estes instructions that I’m reading after the fact. I did get it right anyway, though.
Now for the motor retention. I cut the head off a 1½” #4-40 screw. I glued it into the gap between the tubes, at the non thrust ring end. And then I glued the third tube on top.Not only does the epoxy hold the screw in place, it and the screw fill the gap between the tubes, so I won’t have to worry about stuffing that later.