What would be the worst thing to happen if I used over burn?
dead drive , dead disc,to make sure you could use nero to check your media to see how far it may go but first check to see if your drive can actually overburn.
Although there are warnings about overburning possibly harming a burner, this is extremely unlikely to happen.
I can’t recall a verified instance of this occurring, although it is not impossible.
If you know that your burner can overburn and stay within its capabilities, there shouldn’t be a problem.
If you stay within the overburn capacity of the disc, you shouldn’t produce a coaster.