I've got this 2 bike version:
http://www.bikerackshops.com/TU912K.html
Recently took a 350 mile (one way) trip with our bikes on it. It worked great.
There's also a 4 bike version:
http://www.bikerackshops.com/TU914K.html
which it sounds like you'd need. I can't tell a lot of difference between these
and the one you are looking at aside from the latches that let the rack fold down and out.