I need some help determining what lazy slug tube size to try out. Most of the posts I've seen are of people using the large size with synthetic quilts, and I haven't seen any size specs for people with down quilts.

I'll be packing the following into it:

HG 20* Phoenix UQ
GoLite 3S TQ (alternatively a Mountain Hardwear Phantom 45* down bag)
WBBB 1.1 Dbl
Misc clothing (down booties/wristies/etc in cold weather)
Optional: BBO overcover & UQP

Should I go with a small? Is anyone even using these with down quilts (e.g. does it make sense to do so)?