Sande

I've finished piecing quilt blocks for my son's wedding guest book quilt. I'm going to add a 1 1/2" white border thanks to all your lovely input. The happy couple have decided they want to use leftover fabric for the quilt back. I attached the design they choose for the quilt back design. I feel like I need to sew together four vertical strips to to achieve this look. I'm having trouble calculating what size the center squares should be and what the measurements are to accomplish this design! My brain freezes whenever I try to figure this kind of stuff out!!!

The finished size of the quilt top is 51" X 69" (that's after I add the 1 1/2" border).

Do any of you have suggestions, calculations or advice on how to cut out and piece this quilt back design? I really appreciate any and all your help and will post the finished quilt after it's done!

Thank you for all your help,

Sande