Alright, a bit tired of coming up with fighter pads on the carrier so I'll mess with this a bit. By the looks of that very finely crafted and molded mini ADB released it seems the mechlinks are in two rows of six down the spine of the ship. Which fits with the description "each column of three a-20's".
But it also calls the "bay" or "shuttle box" (in sfb terms) semi external. Now looking at the mini they are completely external if you ask me. Unless of course you consider the warp engine overhead the top of the semi enclosed structure....
If I was to arrange the shuttles in the fashion of the second pic I could fabricate a structure, albiet flimsy, that semi encloses the shuttles. Who's to say the enclosure isn't completed by a force field? Just thoughts....