This is a modification I made to the excellent light bar design by SethBon to suit some aluminium extrusion I have, with external dimensions 7*16.
https://www.altronics.com.au/p/x3249-1m-aluminium-channel-frosted-diffuser-for-led-strip-lighting/
It works well, the length of the extrusion should be 315mm
Print the same as the original, 20%infil with PLA and no supports works well for me.
The author remixed this model.