To clarify, the system is installed in the attic and is lying on its side. The installation is like this: first the heater is installed with the air flow to the right (or the base of the unit), then the evaporator coil (with the apex of the coil facing the heater/heat exchanger), then the plenum with the distribution lines. Does this explanation help?
I have this exact same problem. What was your outcome?
My contractor says he will spin it around so that the coil is pointing towards the plentum instead of pointing towards the furnace.