Centurion Project Part 2 Cosmic Explorer Engine Mount

I'm building the Estes Cosmic Explorer first.
While my focus will be on the interchangable engine mounts in the Semroc Centurions, this post is about the Estes Cosmic Explorer engine mount.
I had heard about this mistake in the instructions and found it a little hard to believe this wasn't caught before thousands of kits were bagged up! This was one on the earlier kits before Estes stapled the instruction changes on the outside of the bag.



Two MAJOR mistakes were made in the instructions.
1. The centering rings and retaining rings were in the wrong locations to fit the TTW fin tabs.
2. The TTW fins were to be glued on before the engine mount was glued into the body tube.

You can enlarge the picture to see the out of order steps.
The incorrect centering ring gluing is on the previous page.

I was changing out the thin blue tube for a thicker, stronger ST-7 tube.
The center hole of the centering rings had to be made a little larger.

220 grit was wrapped around a Sharpie barrel for sanding.

I did a dry fit (no glue) of the engine mount and centering rings to figure out the correct gluing positions.

Enlarge the picture at the left:
Look inside the fin slot and you can see where the rings ended up according to the measurements in the instructions!
Even if the mount were glued in first, the TTW fin tabs wouldn't fit between the centering rings.