I have the seat mounted directly to the chassis (no sliders) using the Brey Krause mounts:
similar to these
https://www.bkauto.com/R_9075_Side_M...o_p/r-9075.htm
Which is funny, looks like they even make a sub mount:
https://www.bkauto.com/R_9032_Sub_St...t_p/r-9032.htm