Estes Honest John, #7240 Build, Part 3, Tail Cone

The instructions are vague about how to cut the fin slots, just a knife and some arrows.

Instead of trying to cut around the corners with a knife tip, I rolled the blade back and forth underneath the rounded end.
Please note: I'm not carving away the entire raised rib. I'm just working around the rounded ends
Then cut the long sides. It's pretty easy to cut down the raised rib.

Most of the slots cut clean except for one.
The inset picture shows the slot with the rough edges.

The slots were cleaned up using a flat file.
Don't do what I did, I opened up the slots a little too wide. The center TTW tab of the laminated fins is only 1/16" thick.