Road race and significant other bench seat

I used to road race my 67 dart, now just local twisties. Still with a split bench seat,with armrest. Had it reupholstered years ago, had them use body colored cloth inserts like the older mustangs had. stops MOST of the sliding around in the seat. Also run a 4 point seat belt, from a Bell helicopter. Run the top belt through the headrest to a reel attached to a reinforced package tray. Works great, and when just driving around, do not need the shoulder belts. Was thinking of putting cup holders in the armrest.