The fin centers aren’t papered (I guess that’s kinda obvious) so were done a bit more conventionally. The one unusual thing was that I cut the interior weight reducing holes by hand, that is, without a straightedge. There’s nothing critical about their size or appearance, so why bother — less clumsy than trying to hold the wood and a straightedge simultaneously. 
(I did have to cut four fin centers, though, because I messed up the first one and it came out too small.)
Then I made sandwiches. Three paper-face-center-face-paper sandwiches. Things did not line up as perfectly as the laser cut Mega Mo fins, of course, but they were good enough. Sanding will take care of the rest. Hopefully without leaving a huge gap between fins and ring. Again.
To facilitate sanding, though, and to keep the edges from peeling up, I treated the non root edges with thin CA. Well, it said thin CA on the bottle, and it used to be thin. It’s at least medium now. But I wasn’t inclined at that point in the day to go running out for thin CA that was thin, so I made do with what I had.
Rich's Rockets 