11 volleys isn't a whole lot when you're talking SRMs. Have you tried downgrading the arm SRM launchers to SRM4+A, and pacing in two more tons of ammo?
Sad to say I usually die before I run out of ammo with this, but the games that work out the best will leave me empty. Perhaps 1 more ton of ammo is a good idea. The reason I used this build is that I figured that the swapped in srm4's will generate heat like srm6's if I understood the grouping right and heat is tight as well. Had there been enough space I would gladly have swapped the MPL for a ML and 1t ammo but that unfortunately....