sounds good. i usually like 3.5 yards for the length for squaring it up, especially from joanns. their wide backing shrinks some but i can still use it. but, if it starts at $10 a yard and goes to $6 with the coupon and i need 3.5, isn't it still costing $21? did i figure it wrong? i trust the width to be square, but i don't trust them to cut. and even at that width, it hardly gives anything extra on the outside.
if the quilt is 98" and the fabric is 104(?)" that only leaves 6" to divide between the two sides. 3" isn't a lot.
UNLESS, the muslin was less $$ and they let you use the coupon. here there's nothing less than $9.99 and if it goes on sale, i can't use the coupon.