If I had the choice you do it would be aluminum all the way. Just make sure you use an aircraft grade T3. Stay away from T6 due to it being heat treated for non cold work (not suppose to bend it). T3 is also heat treated but you can cold work it. As long as you have a compitent tig welder do it. I wish mine was 100 pounds lighter! Try to use as thick of a wall as you can. Some of my suppliers actually offer some 2024T3 with .250 wall thickness. That lets your welder burn it in deep. I would get some tubing with Alclad (anti corrosion) and use zinc chromate as a primer.
As far as strength is concerned, remember the next time your on a commercial airliner that those big ass turbines are usually held on with two to three mounts and of course are manuminum.