Thought I would share an update on getting UOM on my Estimate and SO line items working correctly...
When syncing with QB, Method was having a conflict trying to map 'By the bag' or 'By the gallon' UOM. It was trying to map and sync the UOM on an Item using these phrases rather than the 'bag' or 'gallon' abbreviations.
I had to do a lookup of the UnitofMeasureSet_RecID for the line item, then get the UOMSet BaseUnitName as the value to insert into the line item UOM. This successfully mapped to QB.
Hope this info is useful to others.