I use CCDSoft for subs up to 40min no problem, but I don't think that helps you at all because CCDSoft doesn't support the DSI.
I've never had the same level of success with off-axis guiding as I have with my dual chip ST7. There's many factors that could be making the difference, haven't bothered working through them (not important to me), but I do wonder if long exposure off-axis guiding is practical at long focal lengths with normal amateur gear. There has to be a reason SBIG have gone to so much trouble in their new "coming soon" cameras to support that off-axis guiding with false star.
Roger.