Threw in the towel on the tanks. I cut holes in the back baffles so that each bay is accessable. I am going to reseal the baffle seams and then close up the tanks.
I found two more leaks on the back baffles last week. I don't want to patch them on the outside of the tanks as I think that would leak through pretty quickly.
I had to order eight more plates/rings/sets of screws-nutplates for $200.
Seems like Van's should design the tanks to allow access from outside so you can seal/test/fix and potentially patch anything in the future.