After spending a little time at "OurLads"http://www.ourlads.com/ , please explain your assertion of "undersized".
Yes, there are the occasional freaks of nature in the Pac (UW and U$C have a couple such 6-7, 360 type-freaks, as there are everywhere these days), but as OurLads shows, CU's lines are very much in the median group (as much as you choose to ignore it!), when it comes to size and they've shown they can hold their own when it comes to every Pac 12 team they have faced this season. Where the Buffs are behind is in chronological age, which in a FB program translates to maturity, strength and experience. That comes only with the lapse of time, unless you got some quantum theory to lay on us.
As for DBs "looking back", watching other leagues officiating, "looking back" is becoming less a factor in PI, since DBs are now choosing to break up passes by reading the receivers' eyes and hitting the receivers' hands or the ball as a catch is attempted, particularly on quick "back shoulder" throws. I saw several SEC DBs focus on that aspect without "looking back" and without a negative consequence from the refs. As Pac officiating improves(hopefully), I believe we'll see less of those crappy calls. Looking back helps mostly with picks, not necessarily PBUs.
LBs? Our best, a FR AA, has been sick since camp started, not at all helpful; our best LB recruit was injured pre-camp and the remainder are young, except for Daigh, who is a step slow and Greer, whose mind is elsewhere. Wouldn't be surprised to see a couple of DEs moved to LB, Shaver comes immediately to mind, as does Coleman. With the number of reps now run in practice, combined with their on-field experience, things could improve quickly.
Remember, the players are first groomed to play a high level of college ball, not necessarily to be high NFL draft choices.