Well, it depends on the species. I would try and get the exact type of pleco identified seeing I believe it's mainly just the common pleco that gets massive. I personally have a clown pleco, and the little guy stays under four inches.
Maybe post a picture of the pleco if you don't know for sure what type you have? It could possibly work if you have the right species, and I've sometimes seen pet stores have plecos other than the common variety.
They are still little waste-producers though. In the future I probably wouldn't get a pleco again just because of that, especially seeing cories and such do just as good of a clean up job. Lol, my sand is normally covered in debris only a couple days after a water change and substrate siphon because of Plato.