Hi ! Sorry for the late reply, I've been a bit busy :)

I hear you all, and I will take your advice. I know, DIY supported rails are not the way to go. I hear you. Even if this is not going to work, I think that the profile method was going to work, just not with steel, or made differently with short pieces. I think DIY rail is possible, but you need to get the supports milled from ALU or steel and then tap them. What I am just explaining here is that ROUND fully supported rails don't seem efficient to me cost / strength wise. I've run a couple simulations in SW and that confirmed my idea. You could semi-support a round rail with at least 1/2 of the material used in fully supported chinese rails. Of course, getting those parts machined may be expensive, unless you've got a CNC within hand's reach, or know someone that can get them milled.

That said, supporting the rails with bolts is a silly idea, I agree.