I only weigh off well-regulated actions. The objectives of weighoff are balance and consistency and erratic or inappropriate elements in regulation, including those of friction, inertia, and geometry, will interfere with balance and consistency whatever the weighoff.
Longer, heavier gauge piano strings need larger, heavier hammers to sound good and have sufficient power. Shorter, lighter gauge strings need smaller, lighter hammers. To make the full range player-friendly, the mechanics can be designed to work well without compensation at the light end and with lead added elsewhere as needed.