I am thinking the Blasters will work but may not be optimal for the XP1K. Just trying to decide whether or not I should keep them or sell them. They were not cheap. No doubt about their performance in the dunes with the 900.
Depending on how they affect your RPM with your clutches I would try and run them as they are I guess.
To save some money you could send them to Skat-Trak have them Buffed and glue on 8 paddle Extreme Blades. the Buff will shave off a lot of rubber which makes the tire Lighter and faster since you will Pull your RPM faster.
Last weekend a few friends went to Gordons well and they both have New as of end of last season XP900s and both run Skat-Traks . one has a 26x12 8 paddle extreme and one car has a 28x12.5 14 paddle glider the smaller and lighter 26 tire car would kill the 28 car.
At the Hill Chris with the 26 Skat tire was racing a STU tired XP1k. Chris would beat the guy till the top and the XP1k would finally motor by on the extra HP Barely. So Chris is going to maybe get the Polaris HO kit for the 900 and The XP1k will not catch him ever again at the last part of the Hill.