Brian says:

Is there any issue with bends becoming weak?


No, there is an issue with bends BEING weak. ;-)
Take a sheet of aluminum, bend it 90 degrees, then bend it straight. Now try
to rip it.
See what I mean?
Welding will lose you a lot of strength, yes, but it is a well-documented loss,
and folks will generally use only strength figures for the welded condition.
If you use bent plate, and calculate for the un-welded strength, you _will_
suffer for it.

Steve "not an aluminum expert...."