overstuffing can be misleading .... 2oz is max IMO
any more and there is no real gain 2oz overstuff will give you a few degrees more warmth but 2inch baffles are still 2inch baffles and down can only loft with the airspace provided
some members have taken overstuffed quilts down below there rating but rating will differ from person to person and IMO it's not safe to rely on a 20F TQ in 3F weather
if you getting a 20F TQ with 2oz of overstuff it's still a 20F TQ with a little more down
just my take on it ...