I haven't tried them, but you'd probably be better off just buying a burner that overburns and then overburn decent +R media, as Beall is typically poor media. Also, 4850MB is not the accurate amount, it would be roughly 150MB extra than a normal disc, similar to the amounts that you can overburn most decent +R media. Even if you buy these, there's no guarantee that your drive will let you burn in the extra area of these discs. I think that you're basically allowing the drive to burn in the lead-out area with these discs.
BTW, this thread has no specific relevance to NEC burners and should have been posted in the Media Forum.