I've been meaning to post about this but kept forgetting...
I ended up make a quilt recently with Nobul1 inner and a ripstop outer. Fill was from a down pillow.
The new version, Nobul1, still leaks a little bit still but what does get through are very, very small/thin pieces of down. It's not the clusters that are getting through.
I actually ran out of down as the pillow wasn't accurate on either the FP or fill weight rating so I picked up 850FP for the last 2 baffles (of 16 total. Neither of those two baffles have leaked at all from what I've seen.
Regardless, the amount that does leak does not worry me in the slightest. It's only low quality "down feather blades" that make it through and the clusters, which provide the great majority of loft, stay put...Playing the role of optimist, you could say that it's almost better than it leaks slightly because the "garbage quality" down is going to make it's way out over time leaving you with only the good stuff behind.
*** The Take Away *** Nobul1 works well with 850FP or higher but leaks some of the non-cluster bits found in lower quality down...regardless this small amount of leaking isn't going to cause it to lose much, if any, loft.