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Just as a datapoint. THe fredettes on the 150 are freeking amazing. Grip for days, perfectly easy to back in, and I saw no performance drop in the fluff. I believe it is not so much that you need Marcel type screws, but tall, properly spaces knobs are what give that great all around performance.
The AMA tires are built on those Kendas, which are more like a flattrack tire. Not very deep lugs and minimal spacing. I think that is best for clean ice and also for longevity. I am optimistic that my Fredette Motoz rear will be the perfect tire for me on the 250 (forks are in the shop). I maintain that the Marcel's are fun, but take 90 percent of the learning out of the sport.