I'm looking into our car rental, and right now I can get the Standard/Fullsize for only 10$ than a midsize. However, since there are only 2 of us, we don't really need a big car, but we love to have special smaller car, and sometimes they end up in the higher category (e.g. last year we took a nicely equipped Beetle in the midsize row, much smaller than everything else). If we book the Fullsize, could we take something from the Midsize if there are only Impalas in the larger category?