Originally Posted by
batikmystique
Ditto. It's always better to use a scrap sandwich to help figure out what is going to work the best for the batting being used. It also allows me to check my stitch length to make sure it is what I need with adding the two layers of double fold binding to the three layers of the sandwich - total of five layers (vs the stitch length for quilting when you have 3 layers). Your mitered corners will look perfectly fine as long as you follow the above suggestions for stopping your seam from the edge. Good luck to you!
The practice piece is always a good idea.
When I use a 2.5 inch batting with warm and natural batting - I use a smidge wider than 3/8 inch seam - but I prefer wider bindings.
It also depends on how much you want the binding to wrap around the back - do you want it to barely cover the first stitching? Do you want it to be wider on the back than on the front?