When you agree to do the boom you are agreeing to make a 12.5 block for each person in the swap. Once that has been fulfilled anything extra is just that extra (imo) there are no further "requirements" however keep in mind if your bonus block doesn't fit into the size / colors / etc. of the boom blocks it might not be used in the boom quilt she makes.
Originally Posted by
marija
Guess I'll recheck my blocks before mailing after reading some of the problems with size etc. Do bonus blocks need to be 12 1/2" or can they be any size?