I tow with a '96 Tacoma 2WD. Even with the steel bed, I did not mount the hitch to the bed and sides of the wheel wells like Scamp
recommends. I didn't feel comfortable knowing that the trailer was just attached to the bed.
Instead, I had steel brackets fabricated and welded to the frame just under the bed and then drilled holes in the bed for bolts to pass through the hitch, bed, and into the brackets. This basically sandwiches the bed between the frame and the hitch. I also had the nuts welded to the brackets under the bed so that I can remove the hitch without having to crawl under the truck (although in three years I have yet to remove it). I know several others have done similar approaches. This would probably work with the composite beds if the base of the hitch is large enough to spread out the load on the bed, but I'm sure others will post their experiences.
Because of the height of the receiver on the scamp
(which is not a real gooseneck), I don't think that a hidden gooseneck type hitch will work unless you make a tall custom ball or modify the trailer.
As for the hitch, if you contact Scamp, they will gladly send you a drawing showing how to make the hitch and the minimum dimensions that you have to maintain when you place the hitch in the bed to make sure that you don't damage the truck or trailer when turning.
One thing you may think about is adding air helper springs (air bags) in the rear to help stiffen the ride. This made a world of difference in the stability of my setup. I don't get blown around at all and don't have any bouncing or swaying when I air them up while towing.