Regarding mounting aluminum tanks and crevice corrosion, to me it's crystal clear: Give as much of the tank as possible an air space of something like 1/2" so moisture cannot get trapped against the aluminum, and where aluminum comes in contact with the structure of the boat, it must be completely bedded in sealant that squeezes out on all sides so zero moisture can get into these areas. On a previous boat, I glued 3/4" UHMW plastic strips to the bottom of the tank, then set the tank on the floor of the boat. Done.
The tanks look good - my only comment is that I would have put both draw tube fittings on the aft side of the tanks, since when running the stern is usually lower, and thus you'll get more useful volume. I assume this tank is going to rest on the "floor" you've made, and the tabs are only holding it from sliding around, not taking any of the vertical stress? Tabs make me nervous because they concentrate loads into small points, especially with 1/8" aluminum, but if you're resting on the bottom you're good. Fuel tanks are a major milestone, congratulations!
Regarding the battery comment above, to be honest, my next batteries will be lithium-ion regardless of expense. Half the weight, way less fussy to charge, take a charge in WAY less time than lead acid batteries, and on and on. The weight savings alone are probably worth it for me.
