I say use what ever you can! Waste not, want not. I know that many longarm quilters say not to use sheets for backings, but I have many customers who do & it's never been an issue. GO FOR IT! You may end up w/a whole clothe master piece! Map it out & give it a try! Or using chalk, draw a grid & do a different technique in each of the blocks! It's only practice right!?! HAVE A BLAST!