I added one on the back of my
Burro. I've had to reinforce it about five times and it's still causing problems. It's just a lot of weight leveraged way out behind the
tires on a mild steel frame. It's hard to get everything stiff enough to support the rack.
On the plus side, it hasn't caused many problems for me with sway. I've got a
battery on the tongue, so that puts quite a bit of weight up front.
It's an awfully convenient spot to have the bikes, but I haven't been able to perfect the system. Last time we had it out (admittedly on some pretty rough roads) one of the bikes swung forward and busted out a back window. Not cool.
Figuring out a mounting system on the front would be better. Putting them inside works pretty well, but then you have to take them out every time you stop, which is no fun.
If I ever figure it out, I'll let you know.