Tom, IIRC...
The platenut goes on the joining strip. The tank gets dimpled for a # 8 screw.
Attach the tank and drill through the holes and joining strip. Take the tank off and drill the tank with the #19 and then dimple for # 8 screw.
The strip will get either K1100-8 or K1000-8 platenuts so attach them and drill for the rivets.
Check the plans, I am sure that it is there, just hard to find.
Kent