I've got one, too, and have never dealt with one before. He's also a soph, done growing at 5'5" (doctor has tested), but only gets mid-60s. He's really not a pitcher at all other than getting the ball over the plate well enough, but fashions himself as a pitcher so I worked with him last year as a FY when he threw overhand (with better velo). He's probably the #5 guy on a staff that really only needs (and has) three much better arms. I think he has gone sidearm in the hopes of finding a niche, but I still feel that niche has to be throwing low to mid-70s at the varsity level, and even then........I just really don't know how to help him other than let him keep working as he wishes. The three ahead of him are comprised of 2 juniors and another soph who will all be back in 2011 as well, so there's really nowhere for this guy to go.
That's all just to say, I commiserate with the OP.