Here's a thread with drawings of a small custom hitch:http://myimiev.com/forum/viewtopic.php?f=14&t=2344
I consider the TorkLift trailer hitch I bought years ago as the most worthwhile mod to my i-MiEV, despite having to lug that 41# around all the time (when I bought it I naively thought I could install and demount it in minutes). Pity they never came out with an aluminum version - as it is, they probably never amortized their design and tooling costs.
EVs: Two '12 Wht/Blu SE Prem., '13 TeslaMS85, three 156v CorbinSparrowsLi(NMC), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab96
Hybrids: 48v1kW bike
Mothballed ICE: Orig.Owner '67 Saab96V4, '88 IsuzuTrooper; '76 MBZ L206D RHD RV