Yes, I can and will properly do them like that. And as all steel tubes already cut before I posted last time, I need to modify their lengths slightly to suit. Even so, instead of square 100x100mm end plates, using a rectangular one, let's say 150x100mm to leave flanges at two opposite edges for screw fixing location will make the bolting operation easier. And again, 100x100mm square plate with screws right at inside corners are the most strong fixing method,still don't know yet in comparison?