Thanks for the warning. I'll take it apart and give the sub-frame my opinion before I bolt something on the top for sure now. I had originally assumed my 31lb bike would be no problem. I won't be riding KaTy M on anything too tough while transporting the Mt. Bike; Just gravel stuff, the rough stuff is what the Mt. bike is for on those days. Trailer seems too unwieldy. I wanna bolt something on.