200 aux tanks transfer into the nacelle tank, just like the wing tanks. I kinda think the requirement to fuel the mains first of a 200 is to prevent someone from filling the aux tanks full, but not the wings. This could cause a problem with the weight distribution in the wings.
When you start a 200 full of fuel, it starts transferring from the aux tanks into the nacelle, when the aux tanks run out the pump shuts off and the wing tanks gravity feed the nacelle.
If you look at the gross weight increase kit from Raisbeck for the 90's, it adds lead weights to the outboard wing to accommodate the increased weight over the center section.
Note on a C90, you have to fill the nacelle tanks before the wing tanks. If you do the wings first, they will gravity feed the nacelles. By the time you fill the nacelles, your wings may well be 50-100 pounds less than full.