I think I understand your diagram up there. Is it a rectangular sleeping bag that is oriented just like it would be on the ground,zipper is on the side with hammock running thru where a person would normally be? Is the velcro hole toward the r/h side of center a head hole/ breathing hole.
The potential problem is see here is how you will cinch it up around the ends. If there is a drawstring channel in each of your endcaps that may help, but I don't know for sure.
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