Overburning is only safe/reliable if it's like a minute more than what it's supposed to carry. Nero's website has a program called CDSpeed or something like that to test how much you can overburn a CD.
And anything overburned, including the CDRs over 80 minutes, have next to no error protection (the extra space is meant for table of contents, etc.), degrades much faster (CDRs do degrade if they aren't burned properly or they are bad brand), and won't be read in all CD players (due to it not being in standard form - I think it's referred to as Redbook or Orangebook audio).
Misanthrope is right, just split it into two CDs, you save yourself plenty of grief this way.