I saw a picture, maybe linked to from on here a long while back, of a guy who cut the tongue and extended it, putting himself a motorcycle carrier on the front of the trailer, but right by the shell. Since it was toward the shell rather than toward the truck, it reduced somewhat the amount of additional tongueweight.
Now that I think about it, I think the guy may have set an Airstream shell on a much heavier frame. But anyway, it worked. Lotta work though.
Actually, maybe it was this one. If not, one similar.