Well, since I have some past expecience with this exact motor. I might be able to help a little more with your decision.
First I must ask if you really want to keep this sled for a while longer, I rebuilt my scr monoblock xlt motor and the next year bought my 600 HO CFI and will be patting myslef on the back for the best decision I have every made. The xlt chassis just plain, well... sucks, sorry to say it, compared to this IQ chassis, heck, the rev chassis doesnt fend well at all against the IQ chassis. Why do you think ski doo is coming out with the rev 2 chassis that nearly matches the IQ? My dad is an avid ski-doo fan and was very disapointed that the prototype rev 2 chassis rode exactly, and he even said a little bit worse than the IQ. I know I am going on a tangent that doesnt follow you origional post I am just trying to tell you it would be better for you in the long run to save the money and buy a leftover IQ sled.
I know how addicting the xlt motor can be, specifically if you have a 95 xlt motor. The fact that you have a 95 almost makes it worth the money spent rebuiling it, in 95 the cranks are were much stonger than the later years.
I debated for 2 years on rebuilding the xcr or build a new seld, and I will say that I am 110% happy about buying an IQ. But.... I also rebuilt the top end on the xcr. So I know you might not have the money to spend on a new sled, and you might not ride as much as I do, I really dont know and will leave that decision to you.
As for actually making the decision on rebuilding the xlt.
First... your compression numbers definatly show that you need a top end rebuild, and my guess is that you listed the compression numbers in order of PTO: 70 psi, middle cyl: 90 and MAG: 120.
That is a suprisingly common combination for a tripple sled. These XLT's actually run about 100 psi on a fairly new or rebuilt motor. But as always on a sled it seems that the PTO side will wear more due to the extra load it sees. Your compression numbers are honestly exactly what I would expet for 11,000 miles.
second... even though its obviously a strong running sled to reach 11,000 miles, those compression numbers are getting to far apart.
Third... should you rebuild the top end? Well.... I rebuilt mine, they were not out of round so we just had it honed out. Which you must do with new rings regardless if you got it bored out or not, otherwise you will end up with pretty much the same problem you have now, in a short time. Also you need to decide if you are going to do the rebuild or if your going to have someone else do it. Because with a tripple cly mono-block, your going to have a frustrating night putting those pistons in the block. If you think about it you have to put in the first piston, which is really easy, then slide the block down to put in the second piston, then turn the crank 1/3 and nearly let the first piston fall out of the block while you try to put in the third piston, You quite literally only have a piston rings depth to work with while trying to get squeeze in a ring and not let another one fall out. My dad and I couldnt get it to work without one other set of hands there. It took 3 people 4 hours to get the piston rings compressed while turning the crank and making sure the other piston didnt slide out. If these were individual block motors, it would be simple to slide 1 in and bolt it down, then move the next, and do the same, and then do the last. But on a mono-block you have to try to do them all at once.
Now dont get me wrong, it is worth doing if you want to keep the sled, but make sure you have a 14 year old kid around with tinny hands to reach in and try to compress the rings while you hold the other pistons in the block.
God, now that I have made somthing simple into somthing entirely to long, here is the simple question. Do you really want to keep this sled or not?
If its not worth it then get an IQ, I gueruntee that your going to thank me until you die.
If you really do want to keep the sled, then with the miles you are at and the compression numbers you are showing then you really almost need at least a top end rebuild. But if your putting that kind of money in a sled that you really want to keep, send the crank case to SLP for the toughboy rebuild on the crank, it will more than likely be worth another 10,000 miles on the sled, not to mention at that point you will have a classic sled that you ride on the trails. Thats like seeing a 1980 sled on the trails today, doesnt happen much but you give the guy that rides it a thumbs up because its cool that its still running, and its a cool classic sled. As far as the pistons and rings go you should buy a Polaris shop manual that details the cly round specs and have a machine shop inspect the cyls to see if they will be worth just honing and putting in new rings, otherwise you need new pistons and a bore job on the block. And if that is the case I highly doubt that you would wreck the crank just because you bored it out, but with the Fuji tripples, your likely to wreck a crank bearing somewhere.