Gonna have a GMVM96 furnace installed, but I can't find a spec for the derate on this furnace. Called goodman, they can't find a figure, so the end result is that their engineers claim there is no difference, possibly because the LP kit is an entire gas valves and burners.. So maybe something is altered in this major change-over so the output remains the same? If there is no derate, then I can use the 60K. If there is derate, then I am borderline and will want to have the 80K installed. thanks.