LH-20A1S Burning @ 16x Max?

Just got a LH-20A1S & I can’t get it to burn @ 20x. Using Nero6 & Verbatim 16X DVDs. Nero CD-DVD Speed reports 16x as the fastest. Is there something I’m missing here?

IIRC, LiteOn’s 20x burners officially don’t overspeed Verbatim but some other media like Taiyo Yuden and MBI.

I see, thanks. I just ran SmartBurn v3.1.16t & now Nero 6 reports 18x. So it’s the media that is holding me back?