Thank you CKCOWL:
Your explaination of using sheets is right on. I too use the cotton flat sheets from WalMart. The Walmart near me has a great color selection. I use the flat sheet measurements to size my quilts. Then I am confident it will fit nicely on the bed.
The lady who does my LA quilting never complains about the sheets.
For Quilts for Kids I can back two quilts with one WalMart twin sheet for $5.00. Can't beat that bargain!