I'm growing melons for the first time too, in one of those plastic walk in greenhouses. I spotted my first set watermelon starting to grow this morning :-)
Interesting to hear about the shading, that's probably why I've noticed the watermelon leaves getting a little scorched around the edges, although the other types done't seem to have been affected. I shall try and put some fleece up tonight to try and shade them a little.
I'm afraid I have no advice to offer as I'm still learning, but I'm really excited I've managed to get them this far, and fingers crossed I'll have at least one fruit to harvest.
I can't remember who sent me the seed, maybe it was you vaca? If so, many thanks again, and I'm glad you're having success with them too.