Overstuff in Quilts

[Gruxxx]

What exactly does overstuff achieve in quilts? Say, for example, a quilt is cut with baffles for 2.5" of loft. This is then stuffed with a theoretical ideal amount of down to achieve said loft, which might provide a 20* rating. Adding overstuff may add a little more loft only to a point, because of how the baffles are cut. Is the intention of overstuff to increase loft within a fixed amount of baffle? Or is it simply help maintain loft (minimize compression) from stuffing / un-stuffing and general use? If you wanted a warmer bag, would you be better off getting a bag with bigger baffles/more loft, or adding 3 oz of overstuff to smaller baffles (ie; a warmer rated bag), which perhaps might result in the same amount of actual down? At some point, you surely pass a point of diminishing return and may even loose warmth if enough air space is pushed out by feathers.

[MAD777]

Overstuffing insures that the down will not shift, leaving cold spots. More down will make a quilt look more puffy, but you are correct that the baffles limit this. Don't be afraid to overstuff.
Many erroneously think that you can't compress down at all without losing some efficiency. This isn't true. Tests have shown that down compressed to half it's full volume loses no efficiency. (see Richard Niesley at BPL). Compressing down, to a point, decreases convective heat losses while increasing conductive heat losses, canceling each other out.

All that being said, you may not want to overstuff all the time. For instance, you may want to shift down in a summer top quilt. If it's cooler out, you can shake more down toward the middle and if it's warmer, you can shake the down to the sides off of you.