Well, I tried a pistol grip impact hammer with a bit ground down to a good
radius. My compressor was a bit underpowered so the depth and width of the
indentations was inconsistent. If the difference were random it would
actually look good but there tends to be lots of ugly grouping of patterns
as the compressor tried to keep up. After half an hour the compressor
seized up anyway... The 12" x 12" x .125" plate of 5052 was also warping as
much as .5" over 4" of the pattern width. Not so good considering the final
piece will be 42" x 106". I'd have a cylinder!
So I tried a needle scaler. A Chicago Pneumatic cheapie with .125"
needles. The difference was dramatic in both consistence in depth of dimple
and amount of surface I could do quickly. The distortion was way less too,
only .25" over 12" of width.
Any suggestions on how to flatten out the sheets after I texture them?
That's still 10.5" over just the width, 26.5" over the length. I tried
reverse rolling the 12" samples through a hand rolling machine without much
luck.
It seems that the 5052 might be dulling the needles as well. Is it worth
trying to resharpen them? Perhaps by grinding them flat again or something?

I'm still open to ANY reasonable suggestion to do this differently.

Sorry for being long-winded, this is really important.

thanks all

Ben