I wont ever run a carbon cord with this much HP....They are like rubber bands and wont last, they delaminate fast.
8DN wont perform like a Ultimax or 8JP....8JP will be fastest on top end as its shortest. 8DN is a fair bit longer and will lose 3mph from 8JP I found. Ultimax will also be a tad slower on top then the 8JP but much closer then the 8DN.
8DN can be setup to work well, but top end will always be less....I am more and more believing that the longer belts will last longer simply due to not being stretched as hard. 8DN is a tough one to snap, its also longest and hardest.
It could be the reason the ultimax lasts longer too, being longer. Hard to say for sure. But for me 8JP being so grimy and dirty I wont run that ever anymore. If I was out speed running for every last MPH sure, but for trails and longevity, the Ultimax seems best for me. 8DN would be my second choice and at half the price, a smarter choice.
BTW I measured 2 Ultimax here....one brand new is 44-5/16" and my other with 900 miles on the clock, is 44-7/16"....Did it stretch? Timken says no way no how. Or are they like all belts, and not all exact same. I used to spend hours at my dealer with my tape measure finding the shortest belts in my speed days. 1/8" difference always from belt to belt was normal, and made top end faster.
Dan