Kind of off on a tangent, but not really:
My wife's church has a smaller bow-front aquarium (probably high 30's, low 40's) with a MASSIVE chocolate pleco. I'm not exactly sure how big he is, but I would guess at least 14" or 16". Let's put it this way. He's big enough that when he lies from back of the tank to the front, his tail has to bend to fit. I've NEVER seen the guy on the glass or anything. Look uncomfortable.... but the owner/operator won't listen to me and insists that he HAS to stay in there to keep the tank in balance.
So, just to be relevant, I know for a fact that the "chocolate" pleco can, and WILL, outgrow your tank.