John,
I would do the posting to the stock file via a business object method than stored procedure.
Mainly because you can encaptulate the method and allow even non VFP systems to utilise the object (if done via a dll) and post the records accordingly.
If the class is in a vcx file, it would also make it easier to send updates to clients rather than updating the dbc files.
Anyway, I used to use the same method u used to update stock in my earlier versions as well. They are extremely reliable, no problems with them at all. Just remember to do a tableupdate() on the stock file if transactions are used.
By the way, I read from earlier thread that u're also working on point-of-sales, let me know more about your experience in relation to reliability of store procedures in a high volume environment.
HTH
Yau