The pic is of the rack I used in my '97 GMC 4x4. It worked great and I liked it a lot. Held 3 planes, at least two were .60 sized (never had more than two), and would allow something like a Ringmaster or Barnstormer under the bottom set of wing supports, or allow a sunshade to slide under. The two rear pieces of PVC pipe slip-fit, and were used to push/pull the rack forward to the front of the box (6' box). Worked well, never a damaged plane. The rack had to be put in the back of the box, then loaded with planes (spans greater than rear hatch on canopy), pushed forward, and aft stuff loaded. I put a cargo bar across behind the planes to let me load an ice chest and flight boxes, etc., adjacent to the tailgate. That allowed me to access cold drinks on long drives, and emergency equipment in case of roadside issues, without unloading airplanes on the shoulder of the highway.
My current truck is a Toyota Tacoma 4x4 "Access Cab" (fake seat in back of cab...but I can lean the driver's seat back and take a nap) and 6' bed. I have a cab-height canopy on it....a raised roof would be better for planes but worse for the canoe. Compromises. I made a real basic shelf for the back, with 1x4's across the bed rails and part of a sheet of 3/8" ply. A sheet of "waffle cut" foam rubber padding, with some extra chunks of foam block the wheels into place. No problems, tho the tail lifts sometimes on corners. Simple to fix, if it matters to you. Properly padded, it's a safe ride, but there's not enough room for 3 or 4 planes. I have carried two .60 sized planes (to Edmonton...1,000 miles) in it, but did it by taking the LG off both and sandwiching them in foam rubber mattress pads. I have had thoughts about making a "dropped" shelf, perhaps with a second shelf. Or a shelf that slopes from side to side, with a second shelf. It kinda depends on the size of planes you like, and how many events you fly. On my trip to Clovis last October, I put the SV-11 on the shelf and the profile F-Twister on top of the camp chairs on the lower level, sitting on more foam. Both planes came through alright, 2,700-odd miles, including some "vigorous" driving.