Kwilter,
It would also be easier if you picked a shorter repeat.
You just need to match the centers for a square. Here's a basic no-math set of instructions (
http://www.rjrfabrics.com/media/file...b8b0ba38a7.pdf).
I do use math to cut mine. The formula is
Length of side + (2 x width of border) + 1" = how long to cut strip for mitered border
So, for example, if the center of my quilt measures 65" square & I am doing a 1" border & a 3" border, I would have:
65 + (2 x [1+3]) + 1 = 74" long strips for my borders -- making sure to cut so the center of the middle repeat lines up with the center of my quilt. Yes, this method is much more wasteful.
Then, I'd seam together my borders, press them & then line up the centers & sew to the edge of the center piece, mark your 45 degree lines, and line up the marked lines. You sew right on the line & trim the excess down to 1/4". They are stunning, but require much precision/attention to detail.