I am making a quilt with uneven borders as we speak. Yes you can have different size borders. The only rule you need to follow is put your sides on first and then the top and bottom or vice versa, not sure if that matters. You will not be able to miter your borders of course. Getting your quilt to be the size you want is a challenge when working with certain criteria, such as donated tee shirts or panels, but it can be done. good luck and would love to see the finished product!