Originally Posted by
oneclick
I'd go with the sleeve.
Even if all the heat treatment is lost, you are going to have twice the material.
It's worth a shot. The problem with a sleeve is then that section is overly stiff with regard to the surrounding rail, and you will then get more stress at the sleeve ends. Cessna Conquests had this problem, a part in the tail failed, they beefed it up, more failures because it was then too stiff for the surrounding structure, they redesigned the whole area and the problem was solved.