Actually, I doubt hes ever going to have a good power to weight ratio. The biggest improvement he could possibly make is fixing the severely anemic part. Its like he's on anti-EPO.

Beyond that I suspect he's pushing too hard on the flats and out of gas in the hills. Aero drag is the worst for lightweight riders. You need to learn just how hard you can push before you pop, then make sure to stay under that on the flats and push when you hit a hill.