I use a 2-1/2" binding with a 1/4" seam. I have had no problems with my quilts and they have been washed. If you want to increase the seam width, you will have to add additional width to your binding. If you want to make a 3/4" seam, I believe that your width will need to be at least 3-1/2". Make a test piece, baste it on, and see if you like the look.