First of all, I'd like to say a BIG thank you to everyone who has commented on part 1 and part 2. This has been quite a leap out of my comfort zone in several ways, not least of course is that it is a long way from meerkats!
Reading your suggestions and opinions has really helped. Nicole's comment yesterday "go for odd" made me rethink my basic "framing" idea, because I think I was subconsciously trying to make it look like a "proper" frame, which is why I was anxious about wood length and joining at the corners.
So I've added crochet "struts" to attach the knit to the wood and reduced to 2 pieces of driftwood because it's the weight of the wood that draws out the lacing - I can't do that sideways!
I like the way the zigzaggyness (new technical term) of the crochet echoes the waves and the seagulls and the roof of the beach hut :-)
Thanks for helping me work this out!