Sounds like you're sucking the heat out of the stove.
My unit doesn't have an adjustment on the direct vent with a shutter, I have a variable speed control on the blower instead. I have my draft set at between -0.02 and -0.03.
I've not been able to run the stove long enough at full fire to see how close the burning coals get to the front of the grate because I can't stand it when it's 90 degrees in my basement. However, even at a 5 or 6" long fire, the exhaust is barely hand warm.
I have determined, however, that Keystoker changed the design of the stoves significantly since mine was built. I believe I have a superior heat exchange system to get the heat out of the exhaust gases and into the convection air better. But, my design is also very prone to filling up with fly ash and it's very difficult to clean properly unless you can tip the stove upside down and sideways to knock it loose.
All I can say is that we've been in the 20s, 30s, and 40s this week, and I'm keeping 2800 s.f. at 68 degrees across 3 floors and I've not burned 100# yet since Sunday morning. Yes, it's a new, well insulated house, so that really helps, but the amount of heat the stove puts out even just idling is impressive.