looking for anyone who has a luggage rack blueprint... i took a job out in Montana and besides my bike going on my roof rack, I would like to make a luggage rack to put a backpack or two in

i'm thinking something similar to this...
https://www.discountramps.com/cargoI...ge-rack-10.jpg

anyone have any experience or expertise on this subject? Any problems while building one? my cousin has a machine shop and welder so the tools are not a problem.