I've done ice-box size water melon, acorn squash, tromboncino squash, and butternut squash on trellis. The water melon was supported with a mesh sling I made out of cord-age. The three squashes needed minimal support because the vine connection is much stronger than melon. As I saw each growing I was able to tie a small loop around the trellis and the stem - using the stem as a T off of the vine. With the tougher squash all you need to do is keep the fruit from pulling down the vine, not keep the fruit from ripping off of the vine.