Oh, dear....another TT/weight/tow vehicle issue. Folks also seem to be forgetting that once they get all their #s together, they still need a healthy wiggle room...for those "just in case" times. OP, that is a huge trailer to think about pulling with your MB. Yep, size matters.
Seems like either a change in tow vehicles or trailers is in order. BTW, never, never assume that the salesman either knows what he's talking about or possibly is bending the truth. Whenever the sentence includes, "the salesman told me...", it's usually wrong. Sorry for the bad news.
