Never seen a short balansae, myself, except a young'un. Closer to 3' than 2, once they get good and comfy. Outgrowing my 24" deep tank, ha, but I love them.
If they were grown in shallow moving water in full sun, they would tend to get short leaves and a lot of coloring. On the Santa Fe River there were Vallisneria growing under those conditions that had brown-red leaves only about four or five inches long. To see a picture, go to the following http://www.aquatic-plants.org/galler...4/PC_Santa_Fe3.
I will find out in the next month or two how long the leaves will get under aquarium conditions.
A balansae-loving aquarist on another forum trimmed some of his balansae yesterday and reports the trimmed leaves that came from his 75gal tank were 51" long.