Neil. Ya I looked at the liner actuators, but they take up to much space as there's only about 1/8" thickness to work with.
Steve. looking forward to see how you did the high lift, don't want to steal your ideas but just some pointers would be good.
The radio I'm using is a TH9X Sky Fly. 2.4 . It has lots of switch's and knobs and I bound it to two receivers so I can put one in the trailer to operate the screw drive, brakes, tailgate lock and the lock pin on the turn table to be able to back it up. The transfer drive I was going to model is made by Beall Trailers and you can see the video here.
http://www.beallcorp.com/aluminum-transfer/
It kinda neat as there are no hydro's on the trailer.
Joe Thanks for the comments and I can see where you need the reliability moving all those mountains of dirt. I myself like to push the envelope and try to make things as scale as I can and if possible make them work. If I can somehow make the lift gate work, I'll take those four axles and make up two trailers and that would be even more fun. Keep the comments rolling in and let's see where this end's up.
Rob