Estes Semi-Scale Saturn V, Kit #K-39, Part 4, Marking The Fin Slots

The instructions have you glue in the engine mount then cut the fin slots. You are warned to "cut lightly" because the clear tube is underneath.

I decided to cut the slots before gluing in the engine mount. It takes some pressure to cut fin slots.

Here's how the kit marking guide fit the tube.

GOTCHA: The ends did not fully meet.

Notice the faint pencil lines above the cardstock mount. After marking for the fins, I rotate the guide 90 degrees to see if the four fin spacing is correct. That pencil line to the right is off by almost 1/8"!

I went to payloadbay.com and printed off a marking guide, four fins on a BT-60 tube. This was wrapped and the four fin positions marked.

The original kit marking guide was wrapped on again, and each individual fin was marked for the fairings. 

The kit guide had to be slightly rotated to each correct fin line to mark the A fairing locations.