Hi everyone, I have previously installed a 25' x 25' square made of 6x6s. There are 2 courses and they overlap with 6" offset. They are screwed together top down and at corners. It was originally made (by overcautious dad) for my 3 yr olds swingset/fort/slide and filled with 6" of wood chi...

I should check again to make sure nothing settled. I was pretty anal about building it level originally, though in hindsight I'm not sure why I bothered. I can remove some of the wood chips if I need more board.