I have only used parvula hairgrass, Amano and Florida Aquatic Nurseries tennelus, and glosso as foregrounds. Glosso is the fastest by a long shot. The tennelus's grow fast but glosso is downright annoyingly fast. Althought i like it more than anything else look wise i am just not man enough to slow it down. I think if i would get a baby to lay down in my tank for a week glosso would engulf it.
Vincent, I doubt the folks here know what you mean by HC. I think you should refrain from using short forms unless internationally recognized. By the way, the HC that vincent mentioned means Hemianthus callitrichoides.