You can overburn to ~825MB of mode2 video data onto
some 80-minute 700MB CD-Rs (brands will differ...and even discs from the exact same spindle may differ sometimes). I usually use Fujifilm cdr's (the "made in Japan" ones actually manufactured by Taiyo Yuden) because they are high quality and consistently allow me an overburn of 825MB without
any coasters. Using different brands is a crap-shoot....some may only allow a very modest overburn. The most I've ever overburned an 80-min cdr was 830MB, though I don't recall the brand, nor would I recommend trying to go quite that far because you usually end up with drink-coasters

. One other thing to keep in mind is that it's
possible that your player may not read overburned discs properly if it's fussy.
As for the part about overburning causing damage to your writer, from what I've read, I think that's
probably unlikely. Do a search for those kinds of "overburning" posts on some of the other video forums and you'll find lots of people dismissing these warnings. Of course, don't blame me though if your burner dies because of it!

My burner is designed to support 99min cdr's but I still get this same damage warning from Nero as well

. Seems to me that they're probably just covering their a**es. You could always check beforehand whether or not your burner supports overburning to eliminate any possibility of risk. Here's a listing of some burners that support overburning:
http://www.dvdrhelp.com/cdwriters . Hope it helps.
-d&c