Quote Originally Posted by EddyCurrent View Post
I was thinking I might add a 12mm plate to the flat back side of the gantry to tie it all together. I know some designs have double gantry sides but I'm conscious of the gantry weight and also feel the depth of the gantry cross members will prevent any flexing of the sides. But I may be wrong !

Thanks for your comments
I assume your gantry will be 160mm high, that means for the 600mm travel you will use something like 1m of 160x12mm plate which weights 15kg. For example 1m 160x60x4mm steel profile weights 9 kg and would be stronger than your combined plate+aluminum profile.