I think too it's a neat idea, as it doesn't weigh much and takes little room when not in use, a big criteria in nautical treks.
I'm in for the bivi as well as compared to the tent.
But truth be told, I still have in my mind the idea of a hammock, that could be really fine :
- no more problem with smoothing out the edges,
- no more splashes at night,
- tampering of the chop-related moves of the boat
- little space & weight when stored
- sheltered from mosquitoes
Only problem is how to fit it ?
Some ideas :
- it doesn't have to be of a long span if one likes to sleep on the side (I do), so the approximately 5 feet between the crossbars should be enough,
- hanging it too high is not desirable, what is needed is just the lowest point 2 or 3 inches above the edges when occupied
- sleeping in a fore to aft position should prove really stable
- hanging from the mast with the sail rolled onto it is a no no as it would ruin it
- hammocks simply eliminate the need for a tent as they can wrap you completely (hey, they were designed to offer protection in a pest-infested forest, weren't they !)
- why not some kind of support that would rely on the strong cross bars ? Something like two tubes in an inverted V pointing up ? My only problem is to find some way to keep them from moving fore and aft (I thought about some lines but didn't really find how)