The rules do not require scale airfoil or wing thickness. Fat, skinny, symmetrical, undercambered, it's all allowed.
The 5% tolerance rule for scale refers to the parts of the model relative to each other. Let's say you wanted to build a Hellcat. You couldn't decide what size, so you went to Kinko's and had your three view blown up to 30" span, and also 40" span. If you built a model where all the components are within 5% of the size of the three view, it wouldn't matter if you built the 30" or 40" size. Either would qualify for scale bonus points. If you wanted to use the 40" wing on the small fuselage, that would not qualify because the components were not built to the SAME SCALE (within 5%).
As for Doc and the issue of tanks sticking out the side of the fuselage, the rules allow it. Carrier rule 8.1.2.2 discusses the engine AND ACESSORIES protruding beyond scale contours. There was a rule proposed to change this a few years ago, but it failed. I am sensitized to this issue because I felt it was directed pretty squarely at me personally. Someone complained about my models at the NATS one year, when in point of fact that year neither of my scale class models even had protruding tanks. That's the kind of thing that makes other hobbies look a lot more appealing!