Simon,
i think to knife edge, it should be done with proper equipment otherwise the balance would be extremely out of whack before balancing(lathe,crank grinding machine, etc)-mine will be bad enough. When i send in for balancing, i will be requesting that major balancing be done by knife edging and grinding the ends of the rod journal outers (the non journal part on the sides) first before minor balancing with holes.
I am primarily interested in strength and fatigue resistance. i do not think there are major benefits with knife edging on such a low rpm motor. Now a toyota 1600 turning 10000 rpm, definitely.8000 rpm-worth while, steet car usually run below 6000 and occasionally run to 6500, probably not.If i was going to race it full time-definitely, every 1/2 hp helps.
I just don't like the possibility of paint coming off, plugging oil galleries, the losing my motor. I always consider murphy's law- "what ever can go wrong, will!" I work in engineering, and see too many examples of murphy's. It takes perfect prep before applying paint inside a block for it to be reliable-perfect surface profile/roughness and cleanliness. Nascar teams have every piece of equipment to make it perfect-i don't. Polishing is reliable.