Tartan, I thought with the PP, you'd use the triangle lines to sew the first set of strings to the block. If you do that, you should have a perfect match every time (provided what you drew is accurate.)
After that, you can sew from the top side as the rest of the seams don't need to be anywhere specific.
I'll be finding out soon if the way I'm doing it works well for lining up the triangles. I'm using my Tri Recs ruler quilt a bit for keeping the strips correct. As I sew, I'm going to press to the dark strings and press away from the light strings so I can nest the seams when I sew the strips together. I think I would have done the same if PP, which means I'd have started with one light string as the base, then sewed the triangle so the triangle folds back, then sew the first dark strip. After that, it won't matter.
And based on my experience PP, I'd have also cut my triangles oversized a bit. I hate not having "wiggle room" for PP.
BTW - this is my current PP project that I need to get back to soon.
