I doubt that you will find anyone willing to document something that might become an argument in a lawsuit.
I have been reading the debate of wheelbase length for 3.5 years both here and also at
www.rv.net.
The general consensus, for those that are safety conscious, is:
1. never exceed manufacturers specifications for any limit
2. long wheel base is better than short wheel base, especially when making a panic stop while towing down hill in an off camber tight turn.
If you predict that you will never make a panic stop then the wheelbase probably does not matter.
I have had to make one near panic stop while towing. It felt to me like I could stop just as fast and safely with the trailer as I would have without the trailer. I am happy with the wheelbase that I have and would not switch to a shorter wheel base unless it had an advantage. I do have a relatively long wheelbase.