If the under quilt is hung to close to the hammock body when you lay in the hammock you will also compress the insulation just like a sleeping bag.
The optimal hang for and under quilt would be that once you are in the hammock the hammock body and the under quilt just touch, close enough to eliminate any air gaps that can cause cold spots but far enough away that the insulation is not compressed.
Try to hang the under quilt a little lower. Pan showed me at Mt Rogers that you can move the suspension system in toward the center of the hammock a few inches or pull the the SS a little tighter so that you have more slack in the end with the biners. Make sense?
“Light thinks it travels faster than anything but it is wrong. No matter how fast light travels, it finds the darkness has always got there first, and is waiting for it."