Ivylog, I ran a quick test using the aluminum downspout (lots of quick rigging - need to make it work for testing) and used the 4 gas detection meter from our fire station to test it. Lots of interest there as well, since there is group of campers there as well. With a 1" to 1 1/2" gap we got essentially a zero reading. Right now I'm calling it safe.
Will have to do more checking later on when I build the mounts.
Found I have a leaking lift pump and needed to fix that first before our last outing next weekend. That was an adventure all in it self!