okay, so i took the plunge and bought the best DL discs available, and like any other DL disc, the label says it can hold up to 4 hours in SP mode. i am capturing my VHS to my harddrive for transfer to DVD. if I set my Hauppauge PVR-150 to record in DVD SP mode, i can only fit about 2:30 on a DL DVD according to its specs. why is this? is there a way to get the 4 hours of video onto my DL DVD capturing VHS in SP mode?