After being on some very rough roads, the dinette seating would not stay attached to the floor. The screws were striped out of the wood. I tried larger screws and that helped for awhile but the problem kept coming back.
I called Airstream and they recommended the wing bolts. I moved the seats to get to the holes. I drilled (I believe they were 1/2". the size is determined by the area needed to pass the wings through. Try it out on scrap piece of wood first.) 4 holes for each bench. I too was also concerned about penetrating the tanks and controlled the drill to go through but no farther. There was fiberglass under the floor
I cut the bolts to length. Long enough to go through but not excessive.(again concerned about hitting something) I put the bolts with a washer through the seat supports, added the wings, and pinched the ends of the bolts with aside cutters.
Having the ends of the bolts so that the wings will not vibrate off when the tension is removed has allowed me to re-tighten a number of times.
Some of the holes had steel under them. On these I drilled a small pilot hole and after the bench was down put in self tapping screws of the right length.
The electrical box had to be removed to get access to the rear bench support.
I hope this is helpful.
M. Jay Jensen