Gas furnace flame into rocket stove firebox?

Who has worked on a design to use a high efficiency gas furnace nozzle to flame through a 1 1/2" hole in the back wall of the firebrick firebox? I'm in process on my 3rd rocket mass heater, and like this idea, but wonder what happens when the burner heats up and the draft increases. I'm concerned the changing fuel/air mix with heatup would be far more than a conventional gas furnace. My wife and I are 70-ish and sometimes in severe MT cold would like the convenience of turning on a furnace to save our pipes when we're gone. We love our rocket stoves!!

Emily: How big! On how many levels ?

Thanks for the feedback!
Well, chagrin. I'm dumping the gas idea. Our barn house totally is 40 X 60, made mostly of ICF's. My rocket stove has a firebox 6" wide and 8" deep, about 26" long. Over half the winter heat needs are met with passive solar. BUT after seeing that in both installations the firebox is the lowest point of the entire floor, even a very tiny propane leak would accumulate and risk a devastating fire and explosion.

Because of that, no propane. I will install a backup heating loop into the pex floor loops from a conventional 40 gal or better electric hot water heater. The primary source of heat for this floor loops will be the RMH. The new house will be 32 X 52, also with over half the winter heat needs met with passive solar. A similar installation is what I would put into our existing barnhouse, if a really bad winter comes up or my health doesn't hold up to cut firewood for my RMH. I burn LOTS more and don't like it when we go a week with no sun and the temp doesn't climb to thawing. It's much better to have 0 in the daytime and full sunshine.