That's one of the problems, Guy, that has caused us to ban cameras and phones while riding our trains. The other problem is people 'leaning into' the curve thinking they are helping, when in reality all it does is unload the outer wheels causing them to ride up the rail and derail the riding car.
Our riding cars are quite substantial, weighing around 100kg, so no problem when loaded with 6-8 kids but get 2 adults weighing 100+ kg each and it becomes an issue.
We want to impose a weight limit but rather than pick some arbitrary number we were hoping for a bit of science to guide us.