Why not found what freq the hump is at and ask RPG to make some traps for that freq?it maybe the best £300 you'll spend,they're not that big either, 60cmx60cm.I don't think foam is the answer to your problems,but bass traps.

   RPG foam help my treble and mids an great deal,but still had a few freq humps foam wont cure.only bass traps.