As it happens, I found the DVD SP setting by chance. I have to say, clips rendered from Hi-Def content like AVCHD or MP4, actually scrub up quite well when rendered to DVD SP. Using DVD SP I'm able to squeeze two hours onto a standard 4.7 Gb DVD(single layer). I don't use dual-layer discs for anything other than file storage as the last time I tried to burn a dual-layer DVD, only the computer would play it(yes, it had been "finalised"), domestic DVD players will quite readily accept and play commercially-made dual-layer discs)My Harry Potter movie collection proves that), but they "spit the dummy" on home-burn dual-layer discs. So, for that reason, I keep it simple... DVD SP, burn to single-layer and fit 2 hours + onto one disc.
Cheers!
Neil.