Did some experimentation with the tandem INSIDE the Flex the other night. Being a Cannondale L/S with flat bars and bar ends, it was tight, and had to remove both seats to get it in. The bike did fit on one side with both rows of back seats down, as well as the front passenger seat. It's too long to lay it on its side. Our Bike Friday would fit fine. My opinion is, then, if you want to carry the bike inside a vehicle(unless its small like the BF) the Flex is not the optimum choice.

Here is a pic of the Cannondale stuffed in the Flex, and a few shots of both bikes on top. The new Yakima Rail Grab system works excellent, with some pieces of innertube used as shims to keep the clamp square when tightened. The top of the trays for our single bikes is less than 6", which is a couple of inches lower than on the mini-vans I looked at.