PSU extensions are fine from anywhere, it’s the fully custom ones that you need to be very careful with. Are you looking to do the entire unit from the PSU onward or just extensions as mentioned?
Just doing custom extensions, but was trying to see if I could avoid buying the crimper and doing the pins
You may as well just buy extensions at that point. There are plenty of options available. Check out Performance PCs as I’m sure they’ll have something.