Hey,
I got a quilt project from my blog reader some time ago and i thought you could be also interested in this. The guy wanted to update Climashield Apex filling to 850FP hydrophobic down (I ordered it straight from Cumulus) in his Enlightened Equipment Prodigy -quilt.
I counted the estimated limit temperature and designed baffles for down filling (http://akpojanblogi.blogspot.com/2016/06/quilt-projekti-3-mittapiirros.html). After that i sewed the baffles and stuffed the down in. Pretty simple project and you get a lighter, smaller and warmer product without need of buying a new quilt/sleeping bag or new fabrics. In this case the reducing of weight was about 200 grams / 7 oz, packing size dropped at least 1/3 and limit temperature changed from -1 to -2 degrees Celsius (28 Fahrenheit).
Photos from the ready quilt you can watch here: http://akpojanblogi.blogspot.com/2016/06/quilt-projekti-3-untuvien-pollytys-ja.html (sorry, text is in finnish, but i think photos should also tell the story. Dont hesitate to ask if you want to know more :-) )
Most important thing in this kind of project is that before starting to cut the synthetic insulation out you have to make sure that the fabrics are downproof.
.
