Thanks for the encouragement! I guess I'd be a little happier about it if I was more certain about the header. Its kind of still in a "works for me" state, and Sage Line 50 version 11 is somewhat out of date.

I wonder if anyone has a later version of Sage to test against?
I'll give it some better testing when the stocktake comes around at the end of this month - hopefully it will all go smoothly.