So am I correct in understanding that the amount a player improves in high/high categories is a bit of a crapshoot without any way to predict how high it will go?  I know that PER and LP have a tendency to improve the most, but aside from that, are we all just hoping to get lucky?  I ask because I have yet to have a H/H PER recruit actually stay blue in that category long enough to grow to 80-plus.  Wondering if I am missing something.

Yes, once you get the high-high message, you know it is 28+ growth. Beyond that though, it's just blind luck...high-high could mean 28.01 or it could me 65+ points of grown in Per. 

Your chances of getting a High High PER recruit to gain 80 plus looks to be under 0.5 percent according to this thread (although it might be higher if all the recruits could even increase that high but I can't see it being a very high percentage).

[Edit] Re-reading your post, I'm guessing you are trying to get a recruit above 80+ PER TOTAL (and not increasing it by 80+).  Anyway, that thread will give you a good feel for how much recruits could improve over their careers.

Yeah, I remember that thread, and your edit comment is correct.  Lately, all my H/H PER recruits are going black way faster than I'd like and just wanted to be sure it was indeed blind luck as rednu said.