I'm thinking of doing the same on my Giant Escape 3. Been getting lower back problems as well as pain in the wrists lately, especially on long rides. Figured a riser may be worth trying.

When I asked my LBS about a riser they said the bike needs to be re-cabled. Has anyone had to do this on the Giant bikes when installing a riser?

Also curious if the OP is around, did it solve his problems or not?