If you build a THORJET F20, then I would advise you to buy their CNC cut former set - they are really good quality and it saves so much time and effort during the build. I would also use the thinnest PROSKIN sheeting from Mick Reeves Models http://www.mickreevesmodels.co.uk/ for all the ducting instead of the lithoplate as detailed on the plans.
I have made an F20 with both the built up and the foam wings - make the built up wings - they are easier to fit out.
I also used mini servos to operate all the flying surfaces - I would not go with the bowden cables, they suggest. Finally, I used an OS 46 VX ducted fan engine with the THORJET fan unit, header and pipe.
Build the model as light as possible and make the C/G the same as the plans and you will have a fantastic handling model, which is pretty fast but can be slowed down for really smooth and stable landings.

duthie.