Invert Halo Too possibly? All depends on your budget, but seeing as you're going for a Proto Rail 2011 I'm presuming you're on a bit more of a tight budget. If money is no problem then go for a Virtue Spire.
I have a rail with a rotor (gen2) it works really like a dream, however I have a proto grav fed which works ok if you are strapped for cash about 15 quid new i think