Mike,
Lee's got the idea pretty good....seal....seal....
I spoke with another owner nearby, who just went thru repairing his hatches, of rust or corrosion along the bottom edges. When asked about the contact between aluminum and steel at the edges, he said that they found some sort of "creosote" dipped/saturated material that was between the two metals....of course by now, this material had turned to dust. He mentioned using sealer.....but couldn't provide any further details, other than "I'm never going to wash the car....."! 
As far as insulating the hinges, there is no need for this. At the hinges, you're at steel, welded to steel (at the spine piece) then bolted to steel (at the hatch frame), using steel bolts thru all the bits. So even if you insulated the spine hinge flap from the hatch frame, the thru bolts negate all of this!
The culprit or problem area is where the aluminum skin sits against the frame, or where it is folded over to retain to the frame. These are the areas to be concerned with. Keeping air (contains moisture) off of these areas would seem the goal!
I would think that the GT40 and Cobra guys would be concerned with this sort of thing also, and may be a resource to tap. I will throw a note across the pond and check with a Goose owner who owns a body shop dealing with rebuilding Jags and such other high end cars from the 50's-70's. See how they deal with it!
Steve