This can be fixed in Freeship. First, when doing this, start by creating a new file clone just for the plates. You want to run all hydrostatics in the other file, not in this one. Load the panel into its own separate layer. In layer properties, deselect "symmetrical". Now you only have half of what you need. Use transform/ mirror to get the other half. Make sure you select the "join shared edges" option. I'm doing this from memory, so I might have some of the descriptions a bit off, but that should get you there. Note, the centerline crease which is unavoidable in the original can be eliminated this way. You can also play with heeled hulls this way, albeit in a horribly clunky, time intensive fashion that requires matching the lcg and displacement by trial and error.