on that note, then i'll say this:
the striking surface is not the main row of knuckles, but rather the "flat" area on the fist of the bottom three fingers (between the first and second knuckle). with that in mind, i've been taught, and i agree with this, to line the center of that space (halfway between the first and second knuckle on each of the three lower fingers) up with the center of the forearm.
anyone who doesn't do this ... will be choked out by royce.
in no way am i responding for everyone, particularly folks that know more (maybe they know better, maybe worse, but they do know MORE) than me. i'll stick with what works best for me against a body, a headcage, a wallbag and a focus mitt. that's my suggestion for you -- figure out what feels safest and strongest. it's unlikely that we'll be able to get all the masters together to hit those Bob targets at full power to see whose wrists get tweaked, so until there's some astoundingly obvious solution, stick with what works best for you.