I am not sure what you mean by “ground effects” with a wing on the deck lid. Also it seems like any wing operating in a wake area (caused by the roof) will not yield any predictable (or usable?) results. I would agree that there must be ways of doing simple A-B comparisons that are measurable and repeatable – without a giant recirculating wind tunnel. Another approach involves computer simulations which have probably improved tremendously in the last few years. This is worth looking into although I have no clue in this area.