Size Works Like This
(Okay, I still don't have the +'s to be hit worked out yet--give me time).
Each AP Level of Size gives +10 BLD and +10 DP and some amount of STR to make up for the difference in purchased damage (+5 at Level 1, +5 additional thereafter). This is for Armed.
I need to do the testing for Unarmed (which should be easier) and then start figuring out where we want +'s TBH to come in. I mean, we kind of know that--but the question is where does it start?
Andre the Giant, probably the largest athletic character we could identify weighs in at around 500-550 lbs and is arguably 7'4" (this is, according to Wikipedia, contested--but who cares: what we care about is the gameability of the issue).
Our calculation for height (Uh ... since you asked: POWER (Weight in lbs/47.0.0000107, 1/3)-4) would rate a 550 lb guy at 8'3". He would be at +1 THB HTH and +2 THB Ranged. If we assume that that's worth keeping then it means that probably one level of Size (150 lbs) will get you a +1 TBH by ranged attacks.
I can live with that.