Opinions/Advice on my 800 x600 design

[shoeswith]

Looks great I like the supported rails although what are you planning on fixing them too. It would need to be something quite sturdy and how would it be connected to the main bed of the router.

The other concern I had was with the single central leadscrew of the moving gantry. I think it's pretty likely to lead to serious racking i.e. where there is lateral flex in the gantry. I built one like this and found it quite flexible mine was wood but I still think it applies to your build. I ended up using a pulley system to stabilize the gantry which works well but was an afterthought and was tricky to get right needed a seriously tight steel cable. It seems now most people just use two leadscrews with twin slaved steppers. Given the pretty high spec construction of your build it seems worth the extra costs Good luck with your build.