I recently purchased a solo seat. It is held on in the back with 2 nuts. They looked like hell. I searched for solutions but couldn’t find anything good so I made my own.
I had to find metal dice which wasn’t all that easy. I then drillled them out for a 3/8" insert. The insert has an internal 1/4-20 thread. I used loctite on the sleeve and they work really well.