Wow, nice bed! Do you have drip irrigation under that white plastic mulch?
I'm going to be little help, because it's next to impossible for me to grow melons here. Or any kind of squash or cucumbers either. Bugs and fungal disease have nixxed every attempt I've made.
I did do lots of reading before those attempts, of course. The melons take generous fertilizer to grow a big, healthy vine first, then a huge amount of water when they are sizing up. If they dry out too much (leaves wilt in the middle of the day) before there are lots of leaves on the vines, they will start blooming and setting fruit too early and you'll get small, tasteless fruit.
With a bed that size, yes, I'd be tempted to keep it to 2 or 3 melons per plant so you'll get them big and sweet. Don't forget healthy leaves are what puts the sugar in the melons, so monitor for bugs and disease constantly, and treat early!
