I did notice a few weeks ago that 6 of the 7 Rb's that ran for over 1,000 last year were 225+. The lone outlier was the other Cook.
Obviously fantasy stats are much more then rushing numbers but still only one sub 225 RB'swas top 7 in fantasy, Ekeler, with Kamara and Jones coming close as RB8 and 10 in season total points for PPR.
I would imagine if someone took the time to break it down by BMI that you'd need to get down to around RB36 before you find a RB he might have a higher BMI and ironically that RB is McKissic.
Late to this talk so not sure if people are arguing about his size being an issue but I don't see how it's not THE major concern. The counter argument and one I believe in is that we've seen some of these elite pass catching Rb's have multiple 10+ fantasy point per game seasons just on receiving totals. I'm not sure he can do that because I'm not sure how much he'll be on the field but if he can be that, add in 3-4 fantasy points as runner, then we're talking about a RB who will typically come in that RB 12-15 type range.