I did some sketches here is what I was thinking. Just cheap PVC plastic pipe. I think if you have a tail pin hook to hold the running ship, pull pin, keep lines tight but don't pull in, should go off. Not sure how long the guide rails should by maybe 36" ish, height off the ground say 2 feet?
John, I like the box launcher, seems good for hot combat ships but for flat wingers may need to be a little longer and flatter .
Best, DennisT