I did a search on this topic, because I was looking to ask almost exactly the same question about my MW4 and ORM quilts. I have no issue with the weight of them just the packed size.
As a side-issue, it's interesting how words/concepts can have different meanings on both sides the Atlantic. I think the JRB site says the quilts can be compressed down to "the size of a melon". I think, over here, most folk would relate that to a 'yellow' melon, whereas "over there" I'm guessing the standard would be a water melon?
...anyway...! If I got some compression sacks, how small could I get them for weekend / three or four day trips and not damage them? They're stored lofted anyway. Both those quilts take up a fair bit of the pack.
Apparently, signature that I used from 2006 no longer tolerated so now deleted.
The routine compressed size of JRB quilts top or under by season is
Summers 7x7x5 inches
3 Seasons 7x7x8 inches
Winters 8x8x9 inches
And that is in the original JRB Compression/stuff sack that comes with the quilts... JRB CS come in two sizes...Size regular with summers and 3 seasons, size large with winter quilts and JRB large family quilts.
As stated in several preveous comments, compressing does not dammage the down, especially if unpacked, fluffed and used daily or stored uncompressed at home.
If, when, down appears to loose loft... it is probably time to wash and dry a quilt...Instructions come with each JRB quilt... FTR, I have personnaly washed numberous quilts, one was washed 8 times without detrimental effects/
Ounces to Grams.
www.jacksrbetter.com ... Largest supplier of camping quilts and under quilts...Home of the Original Nest Under Quilt, and Bear Mountain Bridge Hammock. 800 595 0413