A lot of good points pointing about the difference between flat towing & trailering. I guess my test idea was a little too simple.
Regarding my concern or what you are missing: Have you ever loaded a rig on a tandem trailer & started down the road & had it start to sway? Stop, move it forward 6-8" and it trailers fine? This is because you balanced it properly & got the proper tongue weight.
With a single axle trailer, it is much much harder to get this balance just right.
A question further back asked what's the difference between a buggie, boat & jeep. Both the buggie and boat have the majority of their weight almost directly over the axle allowing differences in loading to be insignificant. I don't know the exact number but I would guess 60-70% More in many cases. Let's run with that number for a minute. Figure a buggie at 70/30 and a jeep at 50/50 and both are both 100 inch wheel base. A buggie weighs in at 2000 pounds so it would place 600 pounds of tongue weight. (assuming being measured directly under the front tires) A jeep weighs in at 4000 pounds (minimum) and would place 2000 pounds of tongue weight.
I'm sitting here early in the morning & not going to lay this out exact so give me a little latitude here.
but move the buggie back 5 inches which is 5%. Now your weight at the front tires is 500 pounds..... an 8.3% change.
Do the same thing with the jeep & it changes to 1800 pounds... a 9% change. Percentage wise it doesn't sound like much but it doubles the difference in tongue weight. (the buggie changes 100 pounds and the jeep changes 200 pounds)
So, if you are trying to tow with your light duty SUV and only wanted 200 pounds of tongue weight, +/- 5" goes from double your desired tongue weight to none at all. Now throw in differences of having your spare on or not, 20 gallons of gas or empty (120 pounds), tools, etc, you effect it greatly. Yes, you should be able to place your rig within an inch or 2 all the time.
Again guys, I'm not saying it can't be done. I'm saying I've done it and it wasn't all that simple. The best way I figured out how to do it was determine the desired settle on the trailer hitch. Say 2". I carried a tape measure with me & would measure the unloaded tongue height. Then I would load up and place my jeep on the trailer till the tongue dropped the desired amount.