I happened upon this submission as I searched for wall mounted builds and found your build quite interesting, despite there being no information on wall mounting. A few questions have crossed my mind after reading over your post. The first question is how you intend to keep the horizontal drag chain from slouching, and the vertical from catching the gantry ( if mounted long ways ). I was thinking I would probably just use a basic piece of track like a trim channel that is slightly wider than the drag chain and leverage the slots built into the extrusion to fasten it. The second question is where did you find a T8x3048mm lead screw, and how much? I can see on makerstore I can order custom length 8040 (type20) c-beam (which I would likely do instead of joining pieces if i were to extend my 1515 ) but I dont see that customization option for the lead screws.