A modification to make the good PC open frame to take atx boards and to make it have a proper full pcie support bracket. Also raised the standoffs a lot, so you can use other screws to mount the top to the base without touching the bottom of the motherboard. 

The top uses 9 m3 heat set insets. Do not put them in the pcie support bracket (I used m3 screw there instead).  I used random screws to secure the top to the base and the psu plate to the base. I used m3 screws to mount the psu to the plate. You may need to make/ buy a power button to use if you dont want to carry something metallic to short the power pins (literally any reset switch to 2 slot dupont will work). 

Do not print this in pla or it will warp. No flexible stuff either. Petg seems acceptable, but ABS or the like is better. 

There is an optional bigger base, incase you have more stuff than what I used on mine. It has a ssd mount and space for extra stuff. 

Both the psu shield and original full base are copied into this file set for convenience. 

Remix of https://www.printables.com/model/674535-atx-motherboard-tray-with-m3-heat-set-inserts  to get around the GPL license share alike. (used this model to reference the atx mounts and to use its standoffs.