Maximum size of box section, Stacking box section, Construction Angle

Hello All,

Could one use 100mm * 100mm * 3mm steel box section as X-axis support? If I could get x rails and screws next to each other (twin screw), I figure it would keep down complexity of y axis. Saw kingcreaky had 2 bits of 100x 50 joined side by side. Is either way preferable (i.e. one piece vs multiple pieces)?

And can one stack up in the way kingcreaky went to the side (with a little extra bracing) (e.g. obtain a 200mm high piece by stacking 2 100's on top of each other)?

I'm thinking of a sort of upside down raft type frame.

Any thoughts on steel construction angle as a bracket (the stuff full of holes already)?

I'm looking at weld free designs. Does triangulation do much good if you have a brace on top of your two right angle pieces or do they have to be in same plane to add any real benefit? And if they should absolutely be on same plane, any advice for bolting? Just come down straight through the hypotenuse piece perpindicular to the side piece? Or go in perpendicular to hypotenuse? (Sorry...at work so unable to install anything I can draw with...)

Thanks,

Andy