At a nearby track one organization running there required hardtops to be on, another at the same track required them to be off. In the end, the track rules came into play, which required the broomstick rule, regardless of whether you use a hardtop!
Some clubs that advertise their events as driving schools also require the identical seating and harness on both sides of the car, whether you take an instructor or not. Three point or five, they didn't care as long as it was the same. I now call each club - it's not worth the bad surprise when it's too late.
I did replace my seats with aluminum racing seats - they are more comfy and far lower. In fact, I think I could put the slides back in because they are so thin and still pass the broomstick rule. The other thing you want to ask about with an RT is the use of arm restraints. One club required them also.