This bounce issue is just a matter of getting the correct suspension rating for the load. More than likely, the one you tried was a typical 2000 lbs load rated suspension...ie a Class 1 trailer limit. There are springs or Torflex systems available for 500-1000 lbs setups. Then put a reasonable storage box on and you're good to go.

I have a home built alu tilt trailer for my Tornado which I tow with my Mini Cooper S.

Mike.