Me and my idiot surfer friends used to throw bikes on surf racks sideways and stack for trips to go mountain biking. Worked fine minus some scratches.
If you want to carry both boards and bikes can't you just do some Thule bars with bike attachments on half and strap boards to the other half?
I hate racks for both bikes and boards and end up just throwing both in car, but usually not together. For cross country, unless you are using them on the trip, just ship 'em. Whatever you spend on shipping you'll save in gas and aggravation.