Thats pretty short for a 28 inch draw,but if I was going to try it I would go at least 1 1/2 to 1 5/8
wide at the fads to about mid limb the tapper to 3/8 or so to the tips.I would also probably flip the tip,last 6 inches or so to help with the stacking problem you will get.
Are you sure you draw 28
most say that but to be honest if you watch people shoot very few really draw that with selfbows.
Just a thought.
Pappy