FWIW,
Attached is a notice posted on Attwood's website. I do not recall seeing this notice a couple of weeks ago when I was looking for the specs for my furnace
11-11CheapHeatInfoNotice.pdf
Since the warranty on my Attwood furnace is 2 years it may be another year before I do the cheap heat installation which will allow additional time for research.
Again, FWIW