Update::: Added the 2nd 8" line today, Much different than the single one. more air flow into all rooms, blower motor is noticibly quieter, the return is also quieter, no more excess air is being pushed throught out of every joint on the distribution hookup (where the top of stove hooks to my duct work). I had a flate sheet metal plate made and a single " hole cut into it.
My return is a very short run as my stove is directly below my living room which is the center of the house,The old furncae was upstairs and just used the living room as its return, I'm basically doing the same only with a 10" line.
The furncae is a typical alaska 140 with a 1550 blower motor,
Yes the 16 inch duct would be nice but I only have a single 12" square crossing my basement and 2 12" runs coming from it running the length.
Seems to be working as I have been able to drop my hi feed rate back 2 settings and the house is holding 68 degrees. don"t laugh we like it a bit cooler than the 70+++ we use to get from the wood stove. I remember nights when it was below 0 and we had the windows and doors open to cool off.
I'll take a few pictures and down;oad them later and send out tomorrow..