[aluminum]

Your correct Tig weld is a good way to go . I had this problem on time long ago and went to a welding shop that welded Aluminum every day and where expert at it . They welded my Air Nailer where it had a large crack from being dropped on cement about 4 inches long . I Ved it all out and they welded it for me for $10 since i carried it in to the shop
Perhaps you could trailer your car to such a shop and they could weld it for you out front. Then all you need to do is Grind the weld down flat
my Weld just flowed out like liquid metal and has been working for some years now and is also very thin metal in that area like say 60 Thousands + or -
I would consider drilling the top of the hole out wider just a say 15 or 20 Thousands deep with a larger then the hole drill to get more meat to weld to but ask the experts about that at the shop .
------------------------------------------------------------------------------
TIG (tungsten inert gas) welder. This type of welder uses a tungsten electrode and an inert gas to shield the welding area. The precision achieved with this type of welder is crucial when working with aluminum, especially thin pieces.
Aluminum filler rod. This is the material that will bond the two pieces. Try to avoid using rusty or dirty filler rods, as these will lead to weaker welds.
A canister of argon gas for use as shielding. Pure argon is a cost effective gas solution. 3% helium can be added to increase arc stability.