if we give buckstone 7a+, then undercuts dyno must be at least a grade if not 2 lower.
out of the three classy grit dyno's, the buckstine is MILES easier than the other tow - Deliverance and Undercut Dyno being about the same (although i personally found the undercut dyno harder until after i'd done it once, then it became a doddle to repeat)
so you get that little pockety thing for your left hand?