All ready to put down deckboards. Did lot of reinforcements, and straightening of posts etc. Tricky to get them all to line up right and stay, but with ratchet straps or wedging a 2x4 the right way, or both in some cases, and then putting in the lag bolts and reinforcements while it's wedged seemed to help. I got everything at a "good enough" state. Probably not pass any kind of inspection but I don't need a permit for a deck this low to the ground, and it will be fine in the end.
I think I will want to add built in seating, or flower boxes, or something though, by adding that I will be able to reinforce the rail better, it's still not as strong as I'd like.