Towing Issues: Towing, Minivan, bicycle carrier, spring shop

Question
Hi, i have a 2003 Windstar SEL, with a class II hitch that was installed by U-Haul. Any time i add any weight to the rear of the van (ex. 3 adults in the back seat, or a bicycle carrier, I haven't tried my Pop-up yet)the hitch grinds on the pavement crossing driveways, or speed bumps. What can i do to prevent this? Afterall, Ford advertise that the van can tow. My local dealer said that it's really not true, and that i would essentually have to spend a couple Grand to add a lift kit.
Help, Summer is here, and i need to tow.
Thanks

Answer
The hitch itself is dragging?  Wow, that is one low hitch.

I have a class II hitch that is tucked up so that it only lowers the clearance by 2-1/4".  

I am guessing that Uhaul put on a cheap fit-all hitch.  If you can have Uhaul take the hitch back and put on a better one, that's your best bet.  Otherwise there are helper springs available in the $400-500 range.  Any local suspension/spring shop should be able to give you more information.  

Best of luck,
Shayne Peterson
MobileHitch
http://www.mobilehitch.ca