Try 90 or 99 minute media (but this has some severe compatibility issues).
Or look for othe 80 min media in the hope of finding a better overburner - sounds like it made it through, but the end region is so poor that it becomes unusable.
If you are in the UK, I'd suggest
http://www.svp.co.uk/acatalog/cdr.html - get the CD1020 sample pack - 10 different 80min media (though 1 is RW, and a couple more may just be different styles).
Compare the max overburn using CDSPEED (make sure it's using simulate mode, so it doesn't waste them)
*** CAUTION *** Testing overburn limits WILL cause the drive to run off the leader, this has the potential to damage the drive if it is unable to cope with the loss of tracking control, though drives that don't prohibit overburning should be able to handle this.
Then I'd be inclined to start with the one with the greatest overburn.
The last overburn I did, it started to break down at 80:45, and was completely gone by 81:00 - luck of the draw in media choice.