GUMMIBEAR:
Hiring a camper, and with a GPS....thats a GREAT suggestion ! Save on hotel, taxi, rail costs... etc.
It is also a great idea for Chech abd Slovak republics, where there are some grea looking roadside hookers !
The first person to try it...PLEASE REPORT.
In Frankfurt you can camp out specially at FKK-World and Oase. I am not sure where you would park for the night near PALACE. A trip to Bernd's Sauna would be also a great idea....for the best of the best.