I made this up out of 1/4 ply and just scrap wood and "L" Brackets laying around the bench. The whole cart was assembed with 30 minute and 6 minute epoxy, No scews, nails ext. It is extremely tough so far and launches well with a 20ft 3/8 latex surgical tubing. The contact surface is covered with grip tape from a skate board shop as is the belly of my plane and proved awesome hold power on launch.

I put this up so people could see and maybe take this idea further rather than drag launch there plane or rail launch with elevon style controls as the one in the picture is. Any questions just ask and I'd love to see others people's contraptions too