My heater works great too. Perhaps your core is partially blocked with crud or something. Anyway, Bestop makes a fabric divider called a windjammer that is typically used with the bikini top to make a two seater cab. I have one and it installs easily. You screw in some rails (Like the windshield rail for the soft top) along the riser to the rear deck. The divider uses straps around the sport bar on top and the plastic keepers in these rails to install. It has a big plastic rear window. I've run this set up with the bikini top and the tonneau cover, and the only place I get wet in rain is a little in the gap between the door tops and the sport bar, and the rain runs down the keeper strap for the bikini top to the windshield loop. Not too bad all things considered. It should increase the effect of your heater and warm you up.