Decking plan sketched out - look ok?

Hi, first post here - so please be gentle! I'm an enthusiastic DIY'er and while I've built sheds and other bits, I've not done a deck yet, but I'm a little bit bored (isolation!) and want to have a crack at this myself.

I tend to over-engineer solutions, I'd prefer lean that way to be honest! The deck is a fairly simple rectangle, set on top of an area of lawn now cleared away, to be covered by weed membrane and some gravel to hold it down. Underlying soil is heavy clay and it's pretty wet for most of the winter.

Hope you can view the attached plan, I tried to cover all the info I'd imagine you'd need. It's roughly 1:2 scale = i.e. each square is 200mm.

Thanks in advance!

 

Someone off the forum suggested that those ~3.6m joists running north to south should be supported by a central joist. He said that basically the ones with posts are obviously fine, but the others are only supported at each end. I've attached a revised plan - but what does anyone think? It's a lot more cutting and joist supports to nail in! Or could I put stacks of slabs under the non-post supported lengths?

 

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