yeah, he's not fast and nimble like a smaller WR, but he's not slow and clunky either.
My take is that he doesn't use his size advantage at WR very well, so moving him to a position where he'd be undersized probably doesn't translate well.
I say work on teaching him to use his size advantage better. On the ball that was almost intercepted, if he works back towards the ball (instead of just standing still) and uses his body to shield the defender from the ball, it's an easy completion instead of near interception.