They are not their dimensions. They are the dimensions that I worked out which only require a little attention.
There is already GDIY 51x format which differs from the VPR format that it is 11 slots wide with added + - 24V operation. I now have given all the critical dimensions and the rest is utterly unimportant and left to the manufacturer as long as the final end product rack fits in a standard 19" format cabinet.
No limits in dreaming, but if you think API or Radial are going to read this thread and change their product, then you are being naïve.