The Linex is just a pet idea of mine. There was a thread on safety and best tank location. My suggestion was to look into coating the tank(s) with Linex. Not sure how much weight. Look on Utube for the Linex videos and you will see that everything from an egg to a watermelon to a concrete block survived impact when coated with Linex. Apparently the Gvmt is using it to coat walls to resist bomb blasts. If a tank can't rupture, it gives some addl peace of mind. This probably isn't of any interest to you, but have you considered long travel suspension like the storch and super stol use. Ugly but effective.
I like the way you are thinking your project thru. Going back to what was said, you could also consider NOT going an equal percentage, but making the aileron the slightly larger recipient of the extra area. Still split it up between them, but give the aileron the benefit of a higher percentage. Flying at slow speeds will probably get more benefit from more aileron area. I assume you have taken into account that making the wings,flaps and ailerons larger will transfer more force through each of them and may need
some additional strengthening? Like you, I would prefer the simplicity of the single tank...nothing to go wrong and no additional access holes required in the wings. Have you considered any changes to landing gear to provide more travel/safety in off field
conditions? Also, have you considered having your fuel tanks sprayed with Linex bed liner? This is an idea of mine that I think makes fuel tanks much safer. Its an unproven idea, but if you watch the Linex videos on Utube.