Brian D says:

Add
baffles, I think 20" to 30" apart? Stephen? What's the spec here?

No spec listed, but 30" or so is reasonable. The other thing to make sure of
with baffles is that the size of the holes does not exceed 25-30% of the
cross-section area.
On alu tanks, I would recommend as little plug-welding as possible, say limited
to the top surface. (i.e. build the tank without the top, then insert baffles,
then close) Each plug becomes a hard point, albeit small.

Steve