Just thinking out loud as well, would it be possible that the condensation or dampness is coming from the ground and not so much from the air as suggested? By laying a ground sheet under the hammock and together with the fly might help solve the problem? Its quite damp at times on the coast (rain forest) so it might be a problem that you will have to live with. An interesting experiment might be set up your kit and check the humidity on the local weather station for a few days and see if the problem persists when the humidity is lower or changing?
I'm not sure this makes too much sense.
Surely other have experienced this problem when sleeping near an ocean or body of water.
This is an interesting problem!