The SMB (RB) poptop is much longer than the trailer you are considering.
Are you good at welding? Or do you know a person who can build a frame for this type of trailer?
There would be alot of metal reinforcements needed to mount a SMB poptop to that trailer.
daveb provided some great websites for trailers.
I am considering the Chaser A/T trailer. Way better than a SMB trailer.
If the price is a challenge, get a basic model and add more gear when the time is right.