Right,
I feed my chams in a similar way. I think every animal is different, so if one of them finishes their food very quickly I will offer more until they refuse. I think doing this prevents the cham from feeling starved, which will over all reduce stress. It also prevents binge eating on the rare occasion they get access to a large food source.
With the weighing thing,
say you weigh your crickets... what weight are you going to be looking for?
and how will this indicate the nutritional value of the cricket? you could be weighing fat, not nutrients. In fact you probably are.
Crickets are also fairly vicious to each other, if there is food they will all fight to eat it. As long as you are gut loading properly, then I don't really see an issue with feeding your chameleons that way.
But the weighing thing may be a tad out of line. Its unrealistic to consider weighing each feeder before you feed it. Especially considering each animal will consume each day.