For previous posts you could search this Forum for `bike rack' in the Fifth Wheel section.
For those who have not, as yet, purchased the bikes I recommend Dahon folding bikes which we used for many years when we were sailing. they foldup into a suitcase size and can be stored almost anywhere.
Now we use a Saris Cycle On mounted on the front of our TV for two adult bikes (and tie them down with several bunges) BUT the new ones only have a 1 1/4 inch post with a 2 inch adapter which is not strong enough IMHO.
Take a look at http://www.prolineracks.com/sportrack-sr2902-4ez-bike-racks.html which has a true 2 inch post.
5ers don't seem to bounce as much in the back but I would NEVER carry my bikes on the back of my TT.