What kind of Lite-on reader did you use for your kprobe test? A dvd-rom i.e. 166s or a lite-on burner? DVD-ROM can be inaccurate in kprobes. What software did you use to burn with?
PI should be under 280 and PO 32, I believe.
C't did some burn analysis with 800a - and it tested very good at 2.4x speeds with verbatim, TY, and maxwell.
I know it nice to do both formats, but since it burns so well with + and you have bitsetting (DVD-ROM) and + is about the same price as - anymore, I still not sure why mess with negative.