I'd try it. I've pulled 12v trailers with my 6v truck, but they had incandescent bulbs. I was actually surprised at how well it worked, I figured that the lights would be very dim, but were as least as bright as the ones on my truck, and in fact the flasher still clicked at the normal rate.
I'm not sure how the LEDs would react, but give it a try, and let us know!
