Plextor PX-712A & RecordNow Max (PxEngine 507)

If I want to burn a DVD with my Plex 712 using RecordNow,
I can’t select the burning speed : I can only select max, med and min.

I had the same problem with my NEC2500 and updating my
PxEngine to 507 solved the problem.
I can’t find a newer version from RC PxEngine than 507.

Anyone experienced the same problem ?
Any solutions ?

Pat357

Plex 8/20
Plex 4/2/20
UltraPlex 40x
Plex 12/4/32S
Plex 16/10/40A
Plex 40/10/40A
Plex 48/24/48U
Plex 708A
Plex 712A