Why is the tongue weight so much more on toyhaulers?

A simple answer is that most of the cabinets, tanks, bedroom slides are in front of axle like previously stated. Toys go in the rear and are supposed to be the counter weight.

Ive never heard of the 12% rule. But its almost impossible to evenly distribute the weight. All I know is to put (if you can) the heavier toys up front or over axles and load the lighter stuff towards the rear. Like I said if you can