How far out into the bright running line are you throwing the backcast? With these line styles it makes a huge difference how much running line you allow to extend out of the top guide. Try letting the backcast slip 10 feet into the backcast before the foreward stroke. If still light, try 15, then 20.
If this doesn't cut it for you, consider trying a full sink 10wt WF density comp. You get a lot more flexibility with the amount of line you aerialize with a full sink like than a compact sink head line (teeny, QD, Deep Sea, Depth Charge, etc).