It seems that Filawinder is really set up for 1.75mm and not 3MM, and I just overloaded the original motor too many times.

While waiting for the motors to arrive, I decided to try using both of them, and made a new bracket that would accommodate them to the original back board.

I ended up wiring them in series, and it makes plenty of pulling torque, it will probably now break itself in half if it snagged.
It runs much slower, (probably 1/2 of old max speed) but that isn't an issue as 3mm extrusion will be slower anyways.
(That one picture shows a rubber band that that pulls the motors towards the large gear)

In firmware I changed the puller speed from 25 to 30, and I will probably try 35 for my next run.

I use my Filastruder/Winder/Printer to make R/C airplanes from https://3dlabprint.com/index.php.
These parts will definitely put your printer and filament tolerances to the test.

If anyone wants this dual-motor-bracket, then I will put it up on thiniverse.

I am working on a new way to color PLA Filament with ink-jet-printer ink, it makes nice looking translucent filament, (Magenta and PLA looks like a red/pink champagne)