Please clarify a few things for me.
First, you said that since he can jump up and grab the rim, yet only get his wrist over from the run he needs to work on speed. Are you talking about speed from a running takeoff or the speed of the jump (which is the fast explosion of the jump)?
Second, you said that he needs to work on his speed then later you said that he is one person that you would recommend plyos to because he obviously has the speed component down. Did you mean strength because you said he needs to work on his speed?
I personally think that he has great explosion from the standstill and the weak link for him is jumping off of the run. Something that I'm trying to fix for myself. Certain plyos would be better for him than others. Just my thoughts on that.