If one were to go back to the early days of the forum I posted several detailed postings on guide bushing and several others added even more information.... I also posted tables for oak-park style pc style bushing and common sized router bits. You might want to take a look at:
www.routerforums.com/showthread.php?t=163
for starters then do a search on "guide bushings"
I had posted a few tables in the "gallery" but I think that all got trashed. I will dig up the orginals and post them again if anyone is interested. See post:
www.routerforums.com/showpost.php?p=1812&postcount=9
Ed