I looked at liners, but the weight added puts me close to the warmer bag, and then there's that condensation issue which can be difficult to control unless I sleep in a half open tent, which then asks for the warmer bag again
Currently I think I am taking the -20F bag (conduit shell, so no condensation issues), and the MSR tent, which is pretty large and if I leave the door open, I am probably as well vented as I can be short of sleeping without tent.
Both bags have full length zippers and I usually leave that open and use them as blankets to control heat buildup when it isn't very cold. I think I usually spend 90% of the nights unzipped.
Meanwhile I really lean towards taking the heavier tent. I just recently purchased it and am really dying to try it out. Love the 3-person version that I used with 2 people, so I bet the 2-person EV2 for me alone will be all luxury. The lighter MSR has no floor, and I am not really a fan of tyvek as my only floor on a longer hike when moisture is a constant threat, plus the MSR would require that I take my heavier Black Diamond flip-lock poles, which are almost a pound more than my carbon poles, and suddenly the heavy tent isn't that much heavier...
A +10F or +5F bag with either tent would drop the weight enough for me to shrug off the differences between the tents, but it's just not enough weight saved over the warmer bag, which I know will work perfectly even if I just sleep in the open.
In the big picture, the weight of the bag/tent combo is less important to me than the performance and comfort. I lost about 15 pounds since my last trip and and am in much better cardio shape that a pound or two more in my pack don't really matter - I'm just a perfectionist when it comes to getting my stuff sorted for a given trip.
Time to make up my mind so I can focus on more important things like figuring out how to get from Lone Pine to Yosemite without wasting a full day in Mammoth. If I understand correctly, the Sept 30 weekend is the last two dates the YARTS bus goes over Tioag Pass this year, but the CREST bus doesn't run on Saturday or Sunday...
