Melons and squash...

Hi there... Planning my first SFG and I have a question about melons and squash. I'm in southwest BC on the Coast. One of my SFGs is 4 squares by 6 squares. I'm thinking of using the south-facing 3 x 4-square sections for small pumpkins, spaghetti squash and watermelons. Is 4 blocks enough room for these guys?

I am going to make a little PVC hoop cold frame to put over them so I can get them out early. I can't put a trellis for them because they'll shade the back of the bed, but then ran across this video of this guy using his hoop frame for the plants to vine out on.

(Oh rats! Tried to post the YouTube link but I'm a new member and it won't let me post a link. If you go to YouTube and search for "growingyourgreens" you'll find this guy's videos. The one that has the trellis is named "Growing melons vertically on a trellis...")

I love the way he incorporated the trellis into the hoop frame, so maybe I'll do that next year - but my question is would there be enough room for these plants using the hoop frame covered with something for the plants to vine on?

Thanks for any help... The kids and I planted 4 squares of peas yesterday! Much fun! This is rapidly becoming an addiction!