Might consider using E rated truck tires on the trailer. They will have way less sidewall flex than anything else you can use. If you're using trailer tires, that could be an issue. Of course, more tongue weight is always a good thing if the TV can handle the load. Air bags on the TV can help stiffen the suspension there too.
Since this was "engineered" I am assuming the frame was determined to be able to handle the load..
If I were doing this, I'd have extended the tongue and made room for the harley up front. Then I'd have added the air bags and E rated tires to both TV and trailer.
Or better yet, just get one of these.. http://www.discountramps.com/swivel-wheel-trailer.htm