Gained 30 pounds in college but Velo has not

If you are working with Driveline, be patient.  They know what they are doing.  One thing I can tell you though, if he gained muscle, he needs to make sure he maintains he flexibility.  Lots of stretching/yoga daily.

I know of a local boy who is now with an MLB team(i won't mention the name). They decided that he needed to "bulk up" and he put on 20-40 lbs( i forget how much) and they stopped his pitching and only did weight training. This was all under the direction of the MLB team. His velo actually decreased. Now he has dropped some weight, is more selective on his weight lifting program, back on a pitching program, and his "run and gun" is back up to 106MPH. Our local D1 pitching coach, has told me that just increasing body weight will increased velo , up until the person gets to about 180 lbs. After that there is no good correlation to body weight and velo. I wish i could be of more help, but that's all I know about weight and velo. It sounds like your son has the work ethic to progress. Best of luck.

take it with a grain of salt bc I'm talking about kids who are much younger (2023 and 2022) than your son but my son and his friend both gained significant weight in the past year, partially through working out (and partially through growing up).  my son's velo has gone up and his friend's has flatlined (he's a catcher while my son is a p/inf so we're talking about different throws, too).  my son focused on lower half and stretching in the off season while his friend did a more well rounded weight routine but with the normal (for teenaged boy) focus on upper body and much less stretching. both gained about 15 lbs but it's in vastly different places on their bodies.