I removed the blowers. I have 1 blower on the whole system, the gas furnace blower. I dont have a single baffle, because the air cant go backwards with this system. Currently on the system, I have 2 returns on the main floor with 5 supplys, and on the second story I have 4 returns and 4 supplys. I ducted the whole system in the house specially for the wood/coal furnace. There are 2 types of setups, Parallel and series. With both systems using the blowers, its parallel. The reason why I chose series, was lets say the coal furnace blowers are running, and the plenum on the gas furnace gets really hot, the gas furnace will kick on. So you had nice hot air with the coal, guess what the furnace blower kicks on and cools that nice hot air instantly. Plus you have to deal with baffles and such. I researched the series installation for quite some time and found thats its the only legal way in canada to hook a wood furnace to ductwork. I live in ohio but thought sounds good. Basically what it boils down to is the wood/coal furnace is one huge heat exchanger for the furnace. My wood/coal furnace is set to kick on at 150 degrees, and off at 85 degrees. This way the only air that comes from the system is warm air.
The only downfall I have found (But never had any problems with it is) If the gas furnace shuts down because through the night, the furnace misfires, then the blower doesnt work, therefore the wood/coal furnace overheats. Either way you have to consider an airspace in the ductwork to the floor joists incase of an overheat. I cant figure out how to shrink my pic to post it on here.