Garden question re. folding trellis for Squash

Hi.....I ordered some tall folding trellises from Lehman's. Does anybody know how much they reduce the space requirement? Like say if mini watermelons need to be planted 8 feet apart, or 6 feet for bonbon buttercup squash, can I halve that? I have limited space and plenty of mulch and compost and trying to fit in more plants.....but don't want to space too close. So anyway, how much does a tall folded trellis compare to spreading out over the ground? Thanks. I'd love to hear from anybody who uses trellises.