Threshold to switch from 20F to 0F setup

[gunner76]

Easier to vent your quilts if you are too warm than try and get warm if you do not have enough insulation

[HillbillyHanger]

I'm cold sleeper as I'm on blood thinner, but I've found success with the cottage made quilts fairly close to their ratings, depending on wind. I've used a Jacks R Better Greylock 3 which they claim is 25F in the mid to lower 20s with little wind and been comfortable. One night the wind starting blowing and the results changed. I got cold and I got up and added my Underquilt Protector and all was good. I've used a Hammock Gear 20F full length fairly close to 20F and been very comfortable. It has 1 oz overstuff. I'm not convinced that adds that much warmth retention as it makes it easier for the down to stay in place and avoid cold spots from shifted down.
On another note, I would be very skeptical of any of the commercial rated quilts, sleeping bags and their temperature ratings as "they seem to be survival ratings and not comfort ratings" unless it was Western Mountaineering or Katabatic. I've heard rave reviews that their products "seem to be rated" on comfort level.