Wow "widley varying results on the same disc", I'd like to try that on another drive.
Well, since the drive was forced to burn at 4X the quality should be good. I'll check the drive in the future when I'm using media rated at 4X, burned at 8X.
I've tried to over burn, but that was a waste. I'm still very happy with the drive. After I use up all this sucky ridata media and start burning at 8X, It'll be like having a new drive