One of the issues with alloy is the HAZ (heat affected zone) around any welding will have a much lower strength than the rest. Some recent posts from Dougal on the subject:
So any high-strength alloy needs to undergo heat treatment after welding, however there are very few heat treaters in Australia, and even fewer who have experience with Al.
To give you an idea, Maxi-Drive used to send a batch of parts to melbourne once or twice a year for heat treatment.

