Ralph, maybe you can take that thing back to the store and complain so you get your money back (good thing you did not use it with zero degree nozzles, that would have caused a lot of permanent damage) and go and buy a Classic for about the same money and later on, get the kit to convert your hammerhead to the mosmatic swivel, plate and spray bar and it will last a long time also.
I cannot believe that Northern wants that much money for that surface cleaner, knowing that commercial units by reputable brands are about the same price.
I agree Ralph, you cannot get into the corners with those huge wheels but even the best surface cleaners will only get you into about an inch or less from the edge but you can tilt the classic on it's edge and let the spray hit the wall (lift up right side some to hit right side wall to get all of the surface) then rinse. With those plastic wheels, they are going to get worn fast when you do a lot of concrete, if they have bearings, they might get a lot of dirt and sand in them fast also.
Feel free to call one of us to ask questions before you make purchases, we can probably help you come up with other ideas or solutions.
Good luck.