I have not done any work with the polymer issues to date. Maybe there are other researchers who have.
When I started my research a number of years ago, there were hypotheses about numbering patterns and print layout that have since been disproven. One hypothesis was that notes were arranged in rows, similar to earlier issues from the Birds series. Another hypothesis has to do with the "mini reams" used by BAI. It was believed that notes in "mini ream" ranges were printed with a separate layout. One of my first discoveries as a researcher was that mini ream notes are, in fact, part of a 45/on layout, and it made sense to assume they made up a row in a 9x5 printing format since there were 5 positions belonging to the mini reams. That is why the bottom row in BAI printing layouts is labelled X instead of I. Subsequent research has determined that the layout is in columns, so the 5 mini ream positions make up part of one column. As a result, labeling the bottom row of the layout as "X" has become something of an artifact of past knowledge, without any meaning.
The concept of "mini reams" has confused many people. But it's a very deliberate numbering practice used by one printing company to create a much larger pattern called a "mega-sequence". Information about mega-sequences is published on the CPM Wiki site...
http://wiki.cdnpapermoney.com/index.php?title=Journey_Series_Mega-SequencesPLEASE NOTE: the Introduction still contains the outdated notion of a mini ream
row. Because the research proving that the layout is actually column-based, I never bothered to update the Wiki to reflect this. Data on physical layouts is published separately in the Wiki...
http://wiki.cdnpapermoney.com/index.php?title=BAI_and_CBN_Printing_LayoutsI cannot seem to fit the notes in my database to the BAI $50 layout in the wiki using the 8000 skip interval with 9x5 layout.
That's because BAI has never used a skip-interval of 8,000. You're thinking of CBN. Remember that notes whose prefixes start with A, B or C only are printed by BAI.
For instance I have the following notes (using the input format for SNDB):
AHV 0033687 78 78
AHW 0036641 91 91
AHV 0073150 78 78
Based on these notes alone, it's obvious to me that BAI is using the same numbering format as on the Journey series. The skip-interval is 1,000. The fact that notes 40,000 numbers apart have the same position number pair (78/78) is
not evidence of a 40/on layout. This is normal. The printers are using 40 position number pairs for a given range of serial numbers, followed by 5 position number pairs for a separate serial number range where you can find notes 5,000 numbers apart having the same position numbers. It's a split numbering layout used to create a "mega-sequence". I wish these things were easier to explain.
The polymer notes are relatively new, so I have not touched the data, especially with regards to the $20 notes.