Adding big deck/ extra axle to a 5er. Carry 4 motorcycles.

the biggest problem I see in doing this is no matter how many axles you add the legal GVW is printed on the side of the trailer and raising it is very difficult in my state ,I don't know about where you are. The addition of axles and tubing and bikes will likely put you over the original GVW. Chances of being caught are slim but you could be stopped and not allowed to continue without correcting the overload situation . This would be one of my concerns.Good luck