^^I am using some Sony AccuCORE DVD+R DL discs and it does dub in high speed, but only in 2.4X max from mfg disc specs. I gotta mention one thing though; my JVC DVD (circa 2001) player states that it would play any type of disc EXCEPT DVD+R types and I remembered when I tried playing a Memorex +R disc, it gave me an error message, but somehow with the Sony Acccore +R DL, it plays fine. By the way and according to Sony, AccuCORE means: Accuracy, COmpatibility & REliability.
I guess what I'm really looking for is when using FR mode is that it mostly defaults to XP mode, then SP. For instance; if I wanted to record a show that is 1:05 min. length, then I would like the first 58 minutes to be at XP, then the rest in SP....mathematically speaking, I'm not sure if that's possible.