Glosso might be happy there. Sometimes it will do great in tanks that are inadequate for it, and sometimes never get anywhere in tanks that are ideal. It's hard to predict if it will do well for you or not. I think it's worth a shot... you probably have a very good chance of success.
The glosso may grow 'up' instead of 'out' under 2.7wpg. For a carpet look you want it to grow 'out' and spread. Glosso is stubborn! It may actually work out for you, especially in the bright areas.