The car was never intended to be run at 8s.
I have seen a bunch of people disappointed that the Kraton experience at 8s isnt great and I really don't understand it. The diffs are way too small and way too loose for 8s bashing, they can take a bit of speed running, but jumping with huge tyres on is way too much for this rig. There is no benefit to it either, it's heavy for a 1/8, but not so much that you would need the extra current capacity that 8s have to offer. I get that some people like to just do, "because I can", but why on earth would you get upset when you find that your toaster makes a crap pizza oven?
Just run it at 6s geared to 50-60MPH and it's a blast. I've had my Kraton for a couple of years now and once you have it all tweaked they really are beasts. Shim the diffs, sling on a bunch of aftermarket parts and just enjoy it for what it was designed to be.