Starting to design out my build, looking for critique

[Chrono]

Long time no post, was busy these last couple weeks, but I am finalizing the build. Pretty much everything is done, except for the timing belts and the electronics layout.

I solved my motor problem by simply shrinking the machine to a tiny 1.8m on the X-axis. This allows the use of the smaller 2010 ballscrews, and, in turn, a single motor.

Other than that, I have been verifying dimensions and hole placements and been putting in manufacturer CAD files for all the rails and screws. I have been putting together some angles for the inside (the yellow one in the left side of the machine in the picture) that I can remove if I need the width and otherwise keep in. Since the CAD file already takes ages to change anything in, I only put in one, to keep the computation time down a bit, but the plan is to have two per column.

I guess I only have 4 questions left:
1. I have seen that people usually use transformers for their steppers, and I understand that that is because regulated PSUs may have problems with the current spikes (at least according to the app notes). I could not find a proper post on how to do it on here though, so If anyone has a good source on that, that would be perfect.
2. How do people usually tension their belts? I am still trying to figure out where to place my tensioners.
3. Where do you even get belt long enough for something like this, and what type of Belt? Using a manufacturerer's tools, I have been able to calculate that my belt would be approximately 4.8m long, for the X-Axis. I have not found closed-loop belt in that size yet.
4. Is there anything you would still change in the design? When I say finalizing, I mean that I am compiling prices and sources for my parts, and ready to pull the trigger whenever I am done and move this over to the build-log section, so this is the "final chance" to change anything, so to speak.


As always, here is a web browser accessible version of the model if you want a more detailed look.