Up to the test site and their procedure.  WABO doesn't address bead thickness or width.  They just require the welding be done in accordance with an approved welding procedure.

When you say MIG, I assume you realize short circuit MIG is not covered any longer in the standard.... taken out several years ago (27-13.7.1).

When you say 3F and 4F, I assume you are refering to the sheet metal test as that is the only one done in those positions. 

16 gauge vertical and overhead might prove a little tricky in other than short circuit!

Also, the sheet metal test should be a single pass, so I don't get why you would ask about more than one bead?