I want to use my Hennessy SS undercover as the top skin of an underquilt, facing up against the hammock bottom, as it is already the right shape and fit. (why reinvent the wheel?) I plan to sew a 3" down insulation baffled thickness with a new DWR cover to the SS which will loft out under. But, does anyone have any reason why the silnylon material of the stock SS would not be down proof? Using the SS would be half the work of making a underquilt, and, I already paid for it. Just wondering. I saw something in passing about quilts, which said to NOT use silnylon with down, but, it did not say why. Does anyone know anything about this?