I would use a plate to move it further back. I typically use fender mounted tail lights for the most part. The side lighting is minimal to begin with. Another possibility is to run a flasher mounted on the seat post. It will bounce off of everything in site and give you added visibility. On all my bikes that I ride at night I have a fixed dyno powered tail light and run a Planet Bike Super Flash for visibility. Reflective sidewall tires/rim reflectors/wheel reflectors add to the side visibility.

Aaron