I usually take out the seat bottom (easy, there is metal hook at teh front edge of the seat) so they are standing on the metal bottom not the leather, and I wrap a cotton towel around the sportcap where they are sitting and then put duct tape on the edge of the towel, all the way around. This is not as slipper as the sportpad... also prevents paint damage. The sportcap will support a Viper upside down, so I would worry about a six year old...
I had a chance to carry one of the Indy drivers in the parade too. These guys are not kidding about a left leg work out. By the end of the parade I almost made a major faux pas when I accidentally let the cluch out when I THOUGHT I had taken it out of gear... nearly flipped one Indy driver (Buzz Calkins) and his girlfriend of the sportcap, and onto the trunk! If anyone could have taken a picture, it would have been halarious.... he grabbed the sportcap, she grabbed him... and I managed to get the clutch back in before Indy was one driver (and girlfriend) short.