Here is my 2-piece HP DPS-600PB server PSU mount to AM8 frame - or other XX20 ALU extrusion frame.
NOTE: The mount works (See the pics), but is a bit loose around the PSU. I will probably yet fine tune the model when I have the time. The looseness can also be fixed by adding some cushion tape between the mount and the PSU. (The 1st iteration was too tight and hence totally unusable. Then I managed to add too much slack to the design. ~:/)
Velleman Vertex PETG
Add some cushion tape between the PSU and the mount to achieve a snug fit, if you like. I didn't.