I have. It is pretty simple. Rip some 2x4's to make the frames and add osb for the mattress support. I know osb is $25 a sheet but it still beats a box spring in price. Used corner supports as well.
I used 4 of these in my cargo tailer conversion. Was going to buy just for the solid welded tubing frames but the treated burlap was so strong I kept it. That was in 2012. Still in use today. Cots