Two books of interest:
The Border Workbook by Janet Kime
https://www.goodreads.com/en/book/sh...order_Workbook
Lots of good discussions/charts for fitting borders and some nice fun and useful borders.
also more math, and a good discussion on Prairie Points
Happy Endings by Mimi Dietrich
https://www.goodreads.com/en/book/sh...-happy-endings