I have an Inferno heater also. Pioneer 1000-3. It works well but . . . .
I've observed two issues that make it hard to get the dab truly warm.
First is the relatively small 1000cc engine doesn't generate the volume of heat we're accustomed to in a modern car or truck.
Second, even with good warm air blowing the Pioneer cabs are not designed for cold weather. I have a Honda hard roof, Honda hard rear cab panel, and fabric upper door panels. At speeds above a crawl cold air flows in over the top of the windshield. The windshield does not fit snugly up under the front of the roof. Cold air flows in around the oem doors. The fabric accessory panels fit snugly and block air intrusion but the lower standard doors have wide gaps and no seals. I added automotive rubber door gaskets around the front portion to block most air but still don't have a tight seal. Cold air also flows in through the shifter plate. The wide slots that allow the shift lever and transfer case lever to slide from position to position allow lots of cold air in.
Larry;'s aftermarket shifter plate attempts to fix that with a rubber gasket.