Tube fin design question

I'm using VCP to model a rocket and calculate the CP. The rocket will have a 32mm OD body tube and a 60mm OD tube fin mounted on four straight fins.

Since VCP doesn't do tube fins, what adjustment can I make to the four straight fins to account for the tube fin. Each fin is 14mm from BT to fin tube. If I increase that by 1/2 the tube diameter 30mm and make each one 44mm, that would seam to work, but that's just a guess.

Does anyone have a adjustment factor I can use?

Thanks...

I might have found my answer TRF posting

The first thing you do in VCP is click Options -> Equation Mode -> Extended Barrowman.

When you declare your fins, you will now find that you have the option of "Ring Tail". I believe this is the type of fin you are trying to build.