We would like to go ahead and start using serial control for our products.  Using a simple example, I have a  few questions hopefully someone could respond to:  
 
We have previously built and shipped five red wagons, serial number 1 thru 5.  We are going to create another work order to build 5 more wagons, serial # 6 thru 10, and ship all those through one sales order.    
 
I think I understand how to correctly use serial # 6 thru 10  in regard to entering work order finished production and releasing/posting sales order invoices. My concern, in this example, is more with serial # 1 thru 5:  
 
1) First, it seems OK that I can go ahead and under the wagon item number, pre-enter serial # 6-10 thru DBA menu SC-A (or serial # up to, lets say, 100, if I wanted to).  Is this practice indeed OK?  
2) It also appears from looking at SC-A, I can enter serial # 1-5 (the five units previously built) and enter the work order number, date received (enter finished production date, I presume) and work order unit cost.  Is this OK too?  
3) If entering serial # for  previously built and shipped wagons is OK, how do I tie those first five # to the invoice number under which those five shipped?  Searching through the SERIAL and BKARINV files, I dont see where the serial number ties to the invoice number.  
4) Any general advice/precautions in regard to using serial number control?  
 
Thanks!  
Mike