I haven't seen or heard anything about where exactly the vents go. I know two to the floor and two in the dash. I haven't seen a copy of the instructions for the unit floating around either. The last I heard which was last week, the heater won't be out to dealers until mid Jan.
I can tell you, that with just my homemade windshield and my hardtop. The "heated seats" really seems to keep the cold at bay even down around zero.
If your planning to go through the warning labels with your other installs, I'd guess it would be a safe bet that a vent won't be through there.