Hey all, I have a Clark nx250 and I just got through checking my rectangular down bag with a double zipper for an underquilt. I unzipped it completely, rezipped at the bottom but moved the zipped section to the corner away from the initial zipping point, OVER the foot end suspension rope, only zipping it about 4 inches, then with all of the bottom edge of the bag unzipped and the entire side unzipped apart from that low corner, with the sleeping bag under the hammock, I used mini clamps to hold the bag along the edge of the hammock in about 4 places on each side. The length was perfect! As the top has a cinch in the bag, I could close it down enough to keep air gaps away while adjusting the bottom zipped portion to fit well also. There was very little space underneath and the down did not compress so it seems to be a great fit. SO.... now I will order a long zipper for attaching Velcro strips to each side of the new zipper, use each side of the new zipper to zip onto each side of the bag zipper, attach the Velcro to the existing Velcro attached to the hammock they put there for their own underquilt to attach to, and I will have an underquilt that secures almost the same was as the Clark one (though not entirely as long but seems to be quite long enough), once I attach some shock cord to each end to wrap around the topside of the hammock, at the cost of only a few extra dollars! So far I love my Clark and it is built well but I already have a hard time explaining the cost of the hammock, let alone adding another $200 for the underquilt. This is a fairly cheap experiment and I have been told on our fine forum here that the actual Clark underquilt is a great fit and great product, but I wanted to try this DIY project just to see, ya know?