Yes, a common issue with 3rd rate and 4th rate medias (Tuffdiscs' CMC cast-offs, Chinese crap, the lower quality Moser Baer, Infomedias, just to name a few) is that you get the best results at the start of the disc and that towards the edge, aparent quality gets progressively worse and more out of kilter.
I used to see CMC MAG as being a 3rd rate manufacturer but they have improved, and to my mind that dubious distinction has many more landfill-quality media makers clamoring for that spot. I now regard CMC MAG as only 2nd rate.
Then again when CMC rejects a disc, it's a VERY good idea NOT to use it, because you're getting into 3rd and 4th rate territory.
With Dual Layers, it's even worse because those are way more sensitive to quality, being that a double layer disc is a much more complicated beast than your regular Single Layer disc. Most CDFreaks would recommmend only Verbatim for DLs, and to a lesser extent Falcon and "That's" Taiyo Yuden.
So with "Tuffdisc" DVDR DLs, you've got 3 things going against you.
- 2nd rate maufacturer
- a brander that pulled the discs from said manufacturers garbage can
- the inherent complexity of Dual Layer discs and burns.