Thrustline Arapahoe C, Part 1, Background and Sizing

I've always liked the OOP Thrustline Arapahoe E design.
This picture is from Rocket Reviews: CLICK HERE
John McClure did the build and review.

The original kit was made for D and E engines. The main body tube was a BT-60.

I picked up a few Estes Monarch kits in the recent clearance sales.
I'm not too hot on the Monarch design, it reminds me of a three fin Big Bertha or the Quest Big Betty in a BT-55 body.
This was one of those kits where the face card advertises: "Water Slide Decals!" The only decal included is the MONARCH name in a smaller size than shown on the face card. Masking and placement of all those silver pinstripes wouldn't be easy.

I bought the kits for parts or a possible kitbash. A down scaled Arapahoe C might put the Monarch parts to better use. This will end up with a BT-55 body tube and 18mm power.

I downloaded the original (BT-60)RockSim file:
http://www.rocketreviews.com/unknown-arapahoe-e.html
and loaded it into Open Rocket:

Some changes were made and component materials fixed. When you use online RockSim files you do have to double check the parts. This file was missing a launch lug, among other slight things.

Continued in Part 2 . . .