About Roy's STR, I believe one of our premisses here is that the characters are capable to access their own stats, and usually are speaking face value, unless they are clearly lying or wrong.
That said, I believe Roy is one of the most "stats-savy" characters, and would be reasonable for him to be able to calculate her strenght bonus based on her weapon type, size and taking a few hits. Or he could just have assumed she had STR 29. The catch, I think, is that, for combat effects, and STR checks, both STR 28 and STR 29 have the same +9 bonus, making them essentially "the same STR" for most purposes.
With that in mind, it would be not that much of a stretch to imagine that Roy could consider that Bertha was "as strong as he is" if they had the same bonus. Thus, maybe his STR should be 28+, not 29 or 29+.
Thoughts about this?
PS: On an afterthought, I really like the Geek Math'ology we do here...