I have made a number of t-shirt quilts. I think that unidirectional quilts tend to be a lot nicer. I have found when working with different size patches that framing them with sashing and background fabrics has its advantages. Another option is to run the patches in "columns" with other patches of the same width. eith sashing in between the columns. Many times I've used pre-washed flannel for sashing. Another trick I have learned is to make sure the stablizer you use is fairly light weight but sturdy.