Stock Transport Order

hi all,

I want some clarifications on STO

My client scenario is that they have to plants A and B. Stock will be transported from plant A to plant B using STO. From plant B they are exporting the product to the customer.

we have done all the settings related to STO. its working fine.but we struck up at one point

in IMG 'Define shipping data for plamts' we assign customer to the plant,but if client has many customers we cannot go to IMG and change customers assignment everytime and it accepts only one customer.

my question is how can we process STO for many customers without going to IMG and changing customer.

and also if we transport product from plant A to plant C,we go to IMG and assign customer.is this process correct?.

regards

Rahul