Hi,
I also do 10 minute runners, but have a variation that jazzes em up a bit.
I cut my center focal fabric 8 x WOF and then add a 1 1/2 inch x WOF coordinating border to each side of this center piece. Then sew on your back/outside border fabric as your normally do.....just adds a little extra to the runner and another 5 minutes.
So you need 1/4 yd of focus fabric, 1/8 yd for the inside border, and the usual 1/2 yard for the back/outside border.
Bev