Hello Bob,, the return cold air ducting is as important as the supply hot air ducting. your house or your rooms are like a balloon,, you can pump air into them, but don't and won't get any air circulation with out a return duct from the room [the balloon].
Insulation on the hot air ducts is important,, expecially when the duct runs through a unheated space that you want to leave 'unheated'' otherwise the duct will loose heat into the space, making it partially heated..
You can actually provide just about the same circulation with one big central hot air supply, and several cold air return ducts placed in the far corners of the rooms.. the heat will travel to the corners and back through the return ducts... It really doesn't matter which way you do it,, as long as you do create the all-important circulation loop... returning the once-heated air to the stove for re-heating. This once heated air is MUCH warmer than the air off the floor in the basement, This makes the stove burn less coal, and provide hotter supply air.. All good things..
I'd plan on putting as much work and time into the cold air return ducting as you do into the hot air supply ducting.
Hope this helps.. Greg L