I don't have much mead experience, but I've heard (from Ken Shramm) that you can expect yeast to ferment about 100 gravity points of a mead. Given that, you'd need to start at a higher OG to have a mead finish sweet - or otherwise stop fermentation.This is true. If you start with a high enough gravity the yeast will reach their limit. I have not done this much, but the last mead I made was 10# for a 2.5 gallon batch, and it finished fairly sweet. Stagered nutrients and degassed with a mix-stir.