here are two links that sort of explain the technical problems that occur in welding aluminum. This talks about 21 century aluminum Scandium and lithium and a lot of the other alloys were not available in the 60-70's when the Alan was built. It goes into the problems of heat treating and what happens if you don't when you weld aluminum. 6061 and 7005 are older alloys from the 60-70's era.
http://strongframes.com/
OH hang the Alan on the wall with the Green Frog and get Donnie a Merckx is my advise.
For what its worth
Chuck Johnston.
Ft Collins