I had a ton of questions about the RZR seats and the fixed doors so I figured I'd add all the info here.
We'll start with the RZR seats. I installed them by just drilling holes into the plastic stock bases. They seem a bit wiggly but the stock seats have a bit of a wobble as well. I haven't put a serious ride on them yet so can't tell if I'll need to add some additional support or if they'll be fine. I think they'll be fine.
When I installed them I pulled them forward to my comfort level (I'm only 5'6") so you could comfortably add 2.5 to 3inches to these measurement
This is from the bed to the back of the seat...showing there is still some room to slide them back if you wanted to
From the back of the seat to the steering wheel is about 16inches and from the front of the drivers dash to the end of the seat is about 10inches
from the passenger side dash to the end of the seat is about 9.5inches but once again I could back the seat up about 3" if I wanted to.