The install of the driver's side seat was not too bad. The adapter base Weller sells fit good. I did have to open up one of the four bolt holes a little to get the fourth bolt to line up but that was no problem. There will be some plastic that will have to go or at least be trimmed. Access to the seat mount bolts can be challenging but again, removing or cutting windows in plastic will open things up enough to get it done. I chose the 1" wider seat due to being a little "Hippy" and found it necessary to cut a window from the tube looped from the B Pillar which has the door latch and fender mount attached to it. I removed about a 5" section between the fender mount location and the door latch hoop. It was then necessary to reinforce the door latch with a 3/4" x 3/8" strap laid on top of the door latch piece back running back down to the B Pillar. There was not enough strength in the latch plate with the piece of tube removed. I am not sure if the standard width seat will fit without this mod. but I doubt it.
The driver's seat is now 3-4" lower which is good since I found the roll bar with my helmet several times during the last race. Lowering the center of gravity is always a plus.
Now, the passenger seat is a whole different animal. I do not recommend the average person attempt to install one of these seats on the passenger side of a stock YXZ. Any other seat that utilizes the existing mounting brackets will be a better choice for the average installer. The main issue is the fuel tank location. Weller makes note that the adaper they sell is for the drivers side only. It sounds crazy but I probably spent 8-10 hours frabricating the brackets for the passenger side. I am extremely happy to be done with it so I can now get back to shock testing before the next race next weekend. The passenger side seat sits lower than the stock seat did but it is about 2" higher than the driver's seat. You will also need to repeat cutting the window out of the tube that the door latch striker is mounted on.