You can lay 'flat' in just about any hammock. The key is to not hang it tight but instead, let if luff and hang low. The Hennessey is cut so you lay diagonally to it's rope vector (is that the right word?), and that flattens you out. I'm a side sleeper and it works great. The only time you are 'bowed' is when you lay in line with the ropes.

Interesting old movie..."Eddie Rickenbacker Story", Jimmy Stewart plays Eddie and is seen sleeping in a hammock, camped under the wing of his "Jenny" biplane trainer. The hammock is supported between wing struts. Jimmy is doing it right!...diagonal and comfy.

This "assym" hammock thing is nothing new. Folks have been sleeping on ships that way for a couple thousand years. Most of rural Mexico sleeps in 'assym' hammocks instead of beds. I have a $10 Mexican hammock hanging on my porch and it's actually adjustable to your body.