I've been wondering the same thing recently. The heaviest khuk I own is a 17" Foxy Folly at 24 oz, and it's fantastic, I love it, but it doesn't chop as well as I'd like. munk and some of the others who've handled many more khuks than I say the sweet spot is at 28oz. Do those 4 oz really make that much of a difference?
I'm in the market for a 15"-16" BGRS, but I wonder if I should go up to 18" and try for that sweet spot. I've been highly impressed by the chopping ability of my FF and 16.5" WWII on limbs 3" or less, but on anything larger I think a hatchet would serve me better. The other day I took on a 5" limb of dry eucalyptus, and it gave my WWII (@22oz) a beating. Took forever to chop, and dulled the edge considerably. So...are those few oz really the key to magical wood-obliterating power?
Sorry to hijack the thread, cucharadedragon. To answer your question, I'd say the ideal weight for a 15" GRS is at least 20-22 oz. But that's my completely uninformed opinion. BAS I dunno, but I imagine AK would be comparable to the GRS.
-Tycho-