Sony RDR VX500 and GX300 owners please help

the manual for the RDVX500 is one of the worst I have ever seen, I need to increase the recording time of a dvd to three hours in stead of two, the nearest it seems to get in the manual seems to have something to do with Timer recording, I did what I thought it was telling me to do and punched up three hours and started the source, it still only recorded two hours and then stopped, how do you change the “speed” (or bit rate?) to increase recording time on a dvd on one of these machines?? thanks

now I dont feel so bad, seems no one else can figure it out either.