Howdy all
On the above site they have a single tire carrier that appears to use the "tow bolt" hole (pic I saw had it mounted on the FRONT of a smart).
Using four (4) of these mounts, you could carry four (4) spare tires (for rallies maybe?).
What's that you say, you only have 3 tow bolt mounts?
Think again.
On the front bumper there ARE two (2) mounting holes, but only one (1) is visible.
Measure from center of bumper to center of mounting hole, then go that same distance the other way, drill (or cut) the bumper and you have a fourth tow bolt hole?