the beams are 160x80x5 mm steel
they will be perfectly flatten at a machine shop not far.
then i wanted to put a flat steel plate of 120x5 mm and on the 2 side beams so the bearings can ride on this.
on the bottem of the flat bar ther will be 2 bearing that are pushed against the flat bar with a spring so its really thight .

the steppermotors would be nema 23 directly to the rack ( the rack is bolted to the flat bar on its side) and behind the rack ther would be a bearing so the gear can't jump a way
what do you think or what should i change

i was also thinking of using the mechmate V groove rails etc instead of the ball bearings.