Mimi--
Could you save the ones that only have 5 pieces and use half of them (so the 3 piece sides), to maybe fill in the edges on the sides of the quilt to make the whole thing rectangle? If you cut the other half of your fabric to fill in the middle with, you might still be able to at least use the good half of these 5 piece ones to make the edges straight.... I hope I am making myself clear! It'd be a shame to waste those ones completely!!
Rachel