I learned a trick from the gentleman that I got my kayak from(
http://www.southwindkayaks.com) as I typically load both yak's myself as my wife is a tiny woman and I'd never ask her so what I did was to put a bar inside the crossbar I slide that bar out and put the front of the yak up on that bar with the back of the yak resting on a old chair cushion very safely, I've done this more times than I can remember the piece of tubing is just common steel tubing from Home Depot a plastic cap keeps it in there til its needed I've never scratched the Mercedes in the process of loading or unloading though unloading always seems to be alittle trickier I know they sell a set-up just like at Yakima thats who made the bars and supports but I like to fabricate stuf instead of just running out and buying one, its more fun when you make it work out.