Several years ago, a friend of mine did something similar, but he cut the cans in half with a bandsaw and nailed the cans down, open side up, to increase the surface that got warm; vented it off to his living room.

There's a solar attic ventilation fan out there that kicks on at 80 dg to move air that might be a good inclusion to the system.

http://www.walkablecommunities.org/

Democracy is two wolves and a lamb voting on what to have for dinner. Liberty is a well-armed lamb contesting the vote.

**ubi apis- ibi salus**