After successfully completing a baffled top quilt this winter using M50 and 900fp down from thru-hiker, I would like to embark on building an under quilt using similar materials.

My question is: are there any tricks to getting the underquilt to be snug up against the bottom of the hammock? I see many designs use elastic draw cord on the head/foot end of the underquilt, and hang onto the ridge line from the ends, but I imagine that there is the potential for some sag to happen in the middle where ones bum/back would be and allowing a separation between the hammock and the insulation.

I'm the only hammock user in my party, and have never seen or examined an underquilt, so don't really have a good feel for how easy it is to get them snug.