migrating from Sovos SUT to GTD

We're migrating from Sovos SUT to GTD for our US sales and use tax engine.  We've had lots of issues but we're down to one primary issue where the Sovos standard functionality passes the invoice id instead of the invoice number to GTD which is a value not visible in Oracle anywhere.  They do offer a partial solution requiring changes to how you do invoice numbering that won't work for all scenarios.  My questions are:

1 - Is anyone that has gone to GTD willing to share if they had a good or bad experience with this?  If you don't want to publish it here feel free to email me directly at