Lisa, love the quilt and the border.
I use pin basting and always have because I have the best luck with this kind of basting. Though I agree, if the quilt is large it is a killer on your back. I also use my closed fist to measure the distance between pins.
I guess at the middle because my experience has been you don't have to be exactly dead center in the middle. I think they only use that as a measurement because you have less of a chance to have the fabric bunching up while you are quilting it.
I would to SID if you have an in the ditch foot for your machine for the bowties, but as said by someone eariler, it will depend on the size and distance of your bowties and the space in between. If you want to stay with the geometric look then an "X" through the plain blocks would probably work. If it was me I would do a meandering stitch on those blocks.
Long winded aren't I??
