I have a 12 ft. aluminum boat that I pull with a long wheelbase dually. I can back it into the water as I can see the top of the motor. I had to build a center bracket that sticks up with a tennis ball so I could see the trailer when backing back down the ramp. I find with short trailers that looking over my shoulder at a center point on the trailer I can pick up on minor movements and make corrections, using the mirrors, not so much.
Black Friday around here, you have to park on the freeway shoulder and hop the fence.