Based on recommendations from other builders, I ordered a set of 3/32" tank dimple dies from Cleaveland. I didn't like the way the dimpled skin and substructure were fitting together, and these are supposed to be useful for fixing that little cosmetic issue as well as for building fuel tanks. We shall see.
Update: The package with the set of dimple dies in it arrived promptly, but contained… only the female half of the die set. Not so useful. I called Cleaveland on the phone, and they said they'll send me another set ASAP. Good customer service.