@Mr. Dave 's comment about "tongue weight" got me thinking about how misleading the whole "tongue weight" meme is. I thought I'd relate an anecdote that I hope conveys how important it is to stop thinking about "tongue weight" and start thinking about the issue of trailer stability more holistically.
Many years ago, when I was racing cars fairly seriously in a failed bid to become a professional, a friend of mine built a very nice, tandem axle, enclosed trailer for hauling racing cars. I joined him on his first outing with the trailer. We loaded both our formula-type racing cars, plus tools and equipment, into the trailer and hauled it with my truck. Being the first time this trailer carried a load, we were careful to load it so that it had about ten percent "tongue weight."
Dan was convinced that a high polar inertia would help stabilize the trailer. He was, of course, extrapolating from the well-known fact that higher polar inertia tends to improve the stability of a car. I was certain he was wrong, because the trailer-tow-vehicle system is a completely different dynamic problem from a single vehicle. (For one thing, with a trailer-tow-vehicle system your main problem is second order harmonics, not first order harmonics.) But it was his trailer and he insisted, so we loaded it with heavier items fore and aft and lighter items in the middle. It was horrible. We towed 120 miles to the race track, unable to go faster than 45-50 mph without the trailer weaving all over the place.
When the time came to go home I convinced Dan that what we wanted was for the polar inertia to be as low as possible. (The theory being that it would raise the second-order natural frequency of the trailer-tow-vehicle system.) We loaded the trailer with the same "tongue weight" as before but with the mass concentrated over the axle as much as we could. We sailed home at a comfortable 80 mph.