Hey FB, Jim here again, from SW. Lot of great responses so far from these guys, I'll still add my .02.
I remove my bellypan at least once a season. It makes cleaning the engine compartment a helluvalot easier. I've never stripped the screws yet, but I remove them like Greg B does. Remember the order in which you remove them...I believe something like the first two and last two on each side are a little longer than the rest.
I would also take the skid apart and replace all bearings like mentioned before, unless you're sure the prev owner did it w/in the last season. But if you'll already have it removed to replace the springs, why not replace the bearings?! As for the springs, go with the next largest ones from Cat. Seems to be what a lot of guys on here have done as there are numerous threads about this issue here. I haven't heard enough good about any aftermkt springs to make me not use Cat's.
Definitely replace those carb boots. That might be a sign of the type of maintenance (or lack of) that the prev owner did to his machine

. In all my years, I've never had cracked carb boots, but I hear about them often. The ones in my ZR are still very pliable. However, last year on the first ride my sled wouldn't idle for shit. After a couple trailside stops to figure out the problem, my buddy stuck his head over my motor and saw that one of the carb boot clamps was missing...I forgot to tighten them after cleaning the carbs. :drunk: :banghead: Found it in the bellypan, put it back on, and life was good.
I decided on Cat's coupling kit and was not impressed. All it really consists of is another rear arm that has a couple reinforcing plates welded to it...wish I would have gone with AdBoivin's instead. Someone mentioned that Cat's kit is adjustable, I just don't see that. I never have my blocks in any more, and I don't miss them. As mentioned before, the ski lift is a Cat thing, most wouldn't understand. You can either adapt to point and shoot cornering, or if you ride real hard, learn to slide your weight up on the tank in the corners. When my buddy and I ride (hard) by ourselves, I'm sliding my arse up near the tank in every corner and I have no complaints about my sled's handling.
I would not use the bumper for any extended periods of time for lifting the rear.
87 octane is all this sled requires, and the only gas you should run. Running higher octane may actually deminish the performance of this sled.
I know you already have your risers, but for any other curious souls with this chassis, 3" are the max w/out extending cables and keeping the original handlebars.
I use Tuff Stuff cleaner to clean the seat and it does not harm the green. It's in a yellow/red spray can, and I think it's made by 3M, or maybe Turtle Wax???
Oh, and the harder you ride this chassis, the better it gets, literally!!!

Like someone else mentioned, I've kept mine because Cat nor anyone else has come out with anything to make me trade. The new Apex has my eye as does the Crossfire. If Cat doesn't combine the Crossfire chassis with the forth-coming perf 4-stroker, I'll be on a new Apex in a year or so...BUT, I will not be getting rid of the ole ZR, it will be in the stable for many years to come.