I have a trailer dolly just like the one on the link and it works fabulously for me....on level asphalt
My 16' trailer is probably heavier than most 16 footers and with the 15" tires
the tongue is certainly not level on the dolly. Probably 5-6 inches off level (tongue down) and I'm still able to push, pull the trailer around into it's spot all by myself.
I'm going to check into the BAL leveler too...this has to be easier than backing up on blocks and probably more accurate too, since the blocks are about an inch high each.