Thanks QuiltnNan and Bjbaxter.
Bjbaxter - I literally emptied ALL my scrap bins and made scrappy tops. Totally and absolutely scrappy, the only consistent factor is they are all 6" tall. I can't be sure they've all been prewashed, in fact they probably have not been. I guess fingers crossed!! Since I'm not going to quilt it per se, just do some tacks here and there, hopefully shrinkage won't be too noticeable. I never gave it a thought. Darn.