Good Morning,
It may work but there could potentially be some issues. QuickBooks itself returns the Invoiced QTY on a sales order so if the sales order can't go into QuickBooks the Invoiced QTY will never be correct. In Method through customization you can create an invoice from an estimate and have an estimate look like a sales order.
-Michael
Michael Melo
Product Manager
Method Integration Inc.
Website: http://www.method.me
LinkedIn: http://www.linkedin.com/in/MichaelMelo