I have the same issue with my Circuit. I picked one up from my neighbor for free and really like the way it fits, but I just think my gear volume is too low for what I need for this pack and I keep 'futzing' with the roll top to figure out a way to make it easier and functional. I can see the extra space coming in handy for a winter trip, or where more gear is needed though. I'll be curious to see if anyone has done any mods? I did make a small slit in the top to allow the top strap to go either over the Circuit roll top enclosure, or under. It sounds odd, but with less volume it works better for me to go under the roll top and then the extra material just gets pulled down and clipped to the angled side straps and it is more functional for me. Still too much extra fabric though for my needs.
Ken, are you still upgrading your newly died Starlight? I hope it's working out well for you! I picked up a close out Swift pack from SMD, but I just don't see myself going back to a Z Rest for my sleeping pad, so I haven't even taken it out yet! You did a great job on that Starlight pack, if it's the same one. I wouldn't mind seeing the new mods when they're done!