Ok to add a old 3' x 8"ID chimney piece with on top of a 6" ID piece to test draw?

[ShaneMac]

I'm at my parents cottage and I can not open the door to the wood stove with out smoking billowing out. It is a Supreme Vision and I think it is due to chimney being too short. It is a single story cottage with a low slopped roof and I estimate the stack to be between 10 and 11 feet. Its hard to start and keep the fire going. I would like to stick another 3 feet of chimney on the top but only have a piece from the old chimney which has about 1" of insulation, where the new one has 2" of insulation. The OD is the same for both. For testing purposes would this work to help test lengthen the chimney to see if it increases the draft/pressure to pull the smoke out and draw more air for burning/lighting?

 

[begreen]

The new chimney pipe must be the same as the old. No exception. That might be ICC Excel chimney, but I am not positive.