Mike, I damaged the edge (glass) of a 58" binghams one piece bow right out of the form.....I edge sanded it down to 1 9/16" and completed the build, no problems, the bow shoots great! I only lost 5 or 6 pounds of draw weight which was a blessing because The bow would have come out heavy!
what I'm thinking is if you "glue" a thin piece of soft wood to each side of riser to build it out(shim?) to 1 3/4" so you can center riser on form.. and add a little more thickness to your stack( like bjansen said) you can salvage this riser. Of course you will be grinding the "soft wood shims", core and glass back down to the 1 1/2 plus" riser width. I hope I expressed my thought clearly