tony wrote:

are there general purpose aluminum filler rods that i can use
blindly? an old standby? or is aluminum too sensitive?

The most universal Al filler is probably 4043. While there are better
for some jobs, that's the "do anything reasonably well" alloy. Ernie
says 4047 is better for castings. I plan to get some to try but I have
had success with 4043 even if it isn't the best.

Ted