GURPS 3e: Making a duct-rotor helicopter

[GURPS Fox]

So, I've been working on a CnC Tiberium/Generals fusion setting and one of the things I've been having problems with is designing duct-rotor helicopters (like the SA-2 Samson from Jake Cameron's Avatar) via GURPS Vehicle Builder.

I've been using multiple main rotors but I've been recommended to use concord wing rotors and seen a thread about using multiple coaxial rotors.

Is there any help in this regard?

I'll post a GVB writeup in a moment.