I agree, Mike. We fitted the two largest if I remember correctly, strapped in on the driver's side with the spare tire mounted on the passenger's side of my '66 230SL. There were still, however, a few small spaces scattered around the trunk for things like tools, cleaning kits, spare parts, fluids, covers, work clothes, etc., just in case.
One of my restoration mini-projects was to procure parcel shelves to replace the Kinder Seat when travelling with only two persons, which I did for Meeting of the Clans II. It provided room inside the cockpit for other stuff like jackets, hats, reading materials, and "relatively hidden storage under the "Windschott".
I love that car.
Tom Kizer