tumbler quilt questions

Hi! I'm trying to figure out how to go about making a quick rag quilt for my daughter. I have two lovely coordinating colors of flannel for the front. 5 yards of one and 3 of the other. I found this idea, but have no idea of measurements, and can not find any measurements on line. Anybody do this kind of thing or have any idea how to figure it out?

I would appreciate any help.

http://fabricsnquilts.blogspot.com/2009/10/2009-projects-vintage-chenille-baby.html

Thanks for any help or hints.