The manual for the Flash is posted on the Comp-ARF website and has some good pictures in it. It looks like there is a "quick disconnect" included in the wing tank kit to connect the wing tank to the fuse tank.

As far as fitting other tanks into the wing tank area, the dimensions of the wing tank bay are not shown, but from the pictures, it looks like the wing tank is specifically sized to contain the maximum amount of fuel in that area. Some other tanks might fit, but I'd be willing to bet that they won't be anywhere near 40 oz.

I ran into the same problem with an AD F-16 I'm building for a friend. The "stock" tanks for the F-16 from Jettech hold only 80 oz (40 per side). There is an area inside the fuselage on either side of the turbine that can hold additional tanks, but its not very big and oddly shaped. I looked all over and the biggest "regular" tank I could find that would fit in there was 8 oz. and the fittings would be very hard to get to. Lo and behold, I did some more looking and Jettech has a set of tanks specifically designed and molded to fit into that area and each one holds 20 oz. Problem solved, 40 X 2 + 20 X 2 = 120 oz. total, plenty of fuel for a Titan. Total price of the 2 20 oz aux. tanks (40 oz total) from Jettech, $115...

Bottom line, $114 for 40 oz of additional fuel isn't completely out of line and I doubt you'll find anything nearly that big that will fit...

Bob