Steve,
When I was looking at trailers about four years ago, I was also concerned about the Lance frame. So I mentioned this concern to a competing manufacture when I toured their factory and they sad "follow us". They took us out to their bone yard where there was the exact frame that was on the Lance trailers at the time. Without decking on the frame, it was easy to twist the frame in my hands. Since I anticipated using the trailer on unpaved roads, it was an easy decision for me to not get any trailer that used that type of frame. Yes, the frame will stiffen up considerably when it has a deck on it, but, IMO, the frame is the most important part of any trailer and I was not willing to skimp on it.
Perhaps their frames have been improved in the past four years. I don't know. But if I was to do it again and the frame was still that "wimpy", I would make the same choice.
Hope this helps,
Steve
p.s.; I apologize to all the Lance owners out there as I know you are likely happy with your unit and don't want to hear of possible frame issues. But this was my experience and the engineer in me just wouldn't let me compromise on this aspect of a very expensive purchase.