Bruce, in Illinois, you want insulation. 3/4" straight ply is fine for certain areas, but up by you? No way.
Which way the foil faces is open to debate, and even a lot of plans don't take into consideration WHERE you live and where you're going to use the TD.
Down here in South Florida, I want all of outside heat to GO AWAY, so EVERYTHING faces out, including the floor insulation. Up by you, camping in cold weather, you want all of your body heat to stay IN the cabin, so you would do it the opposite.
Don't know what difference this makes with cheap HD foil-backed white insulation, but...
It can be 90 degrees out here by me, and when I open the door, it's COOL in there.