Had them fail on our desert cars, not like that though. Usually see them start to take a shape at the base between the two springs and crack there. Being injection molded glass filled nylon they are pretty consistent, (but they are a wear item.). I agree that it took a beating and got over the crossovers and it just couldn't take it any more. Your running a pretty heavy secondary, Not sure what you have for a main, but it looks to me that the secondary is doing all of the work. The 7" spring your using has a collapsed length of 4.46". Might want to try backing your crossovers all the way off or remove them completely.
Yeah I've seen sliders wear, just never shatter. The reason it went over the crossover rings was because it split. Those are just pieces that are stuck between the spring & crossover nuts. At fist glance I too thought it got pushed over the crossovers and then broke, but after looking closer and taking it all apart, it cracked and then the coller shattered into 4 pieces. Some of the pieces just got wedged between the crossover nuts & springs.
Yeah it looks like it took a beating but in reality I don't hammer on this car and am not a jumping kinda guy. I will push it through the whoops pretty good, but not with the my wife. & daughter as I get yelled at in the intercom. They are my restrictor plate!!! LOL!
Regarding the front springs the upper is a 7" 325 over a 10" 350. This is the spring rate Walker set it up with. Remember the spring rate is devided when the two springs are working before the crossovers stop the upper spring. The spring rate when both springs are working together is 168.5 lbs. When the upper is stopped you are then working off the 350lbs lower only. The 2 seat cars get a 300 over 350 I believe.
This is also in conjunction with Walkers needle valve internals. Overall the cars is pretty soft, you can push down on the hood and compress the ride hight at least 2 inches. Basically you can push it down till you pretty much hit the crossover nuts. At ride hight i have right around 3/4 inch between the slider & crossover. With the needles the valving is pretty light allowing it to work over the chatter and small stuff and when the needle kicks in it starts to close off the valving.
Biggest issue I see with these cars and why you need such heavy springs is the poor geometry Polaris has put in the front of these cars. The front shocks are so laid down that you have to spring the crap out of them. My old beam prerunner had lighter front springs then this RZR. I was told on the race RZR's like Holtz & Jagged where they stand the shocks up more and relocate the upper shock mounts they can run springs in the 175 upper & 225 lower range. To me that is closer to what I expected. But after measuring as seeing the degrees these shocks are at compared to the arms it no wonder you need such heavy springs.
One of the other cars in our group is a 800 RZR4 and he put the RacerTech springs on his stock Fox Poduim shocks. It made a decent improvement on his car. The lower spring is a 300, which on their spring concept is the lighter spring and their magic secret sauce upper spring is suppose to be their heavier spring. They dont tell you the spring rate on that coil. So even on the RZRS 800's they run a pretty stiff spring.
