Make Plextor PX-880SA Burn Slower

I just bought a Plextor PX-880SA.
I installed the Plex Utilities that came in the box.
I saw the options to change the media speed, but i got errors trying to set it.
I then upgraded Plex Utilities to version 1.2.7. The option to change the speed is not there anymore.
I also upgraded the burner firmware to 1.12.

I bought some average blank DVDs, the burn quality is average. I burned at 6x.
Just wondering there's a way for me to update the firmware to burn at 4x, maybe the quality would be better.

I tried using the MediaCodeSpeedEditor, but can't find the rpc1 firmware for this burner.

Has anyone tried to modify this burner firmware?

Here's the media info from DVD Identifier:

** INFO : Drive = PLEXTOR DVDR PX-880SA - [FW 1.12] - [RAID]
** INFO : Write Capabilities = DVD+R DVD+R-DL DVD+RW
** INFO : Write Capabilities = DVD-R DVD-R-DL DVD-RW DVD-RAM
** INFO : Disc = [DVD-R:RITEKF1]
** INFO : Reference Speed : 1x DVD = 1385 kBps
** INFO : An Writeable Disc Is Recommended For Accurate Results
** INFO : Write Speeds (Supported By This Drive On This Disc) Listed Below

** INFO : GET PERFORMANCE Write Speed Descriptor(s)
Descriptor #1 = 22160 kBps (16.00x) - [CLV/Non-Pure CAV]
Descriptor #2 = 16620 kBps (12.00x) - [CLV/Non-Pure CAV]
Descriptor #3 = 11080 kBps ( 8.00x) - [CLV/Non-Pure CAV]
Descriptor #4 = 8310 kBps ( 6.00x) - [CLV/Non-Pure CAV]

Thanks,

Will