Is it a sheet metal screw or machine screw? I had to remove the seat pan on my Eyra when I was running wiring under it, and all 10 of the screw that held the seat pan as well as the screws that fastened the seat bases, were all machine screws in 1/4-20 thread. The only sheet metal screws I had to remove were 2 on the backs of each of the seats. Can you post a picture?