Hello Viscount13,
Sorry for being late, I had a quick look at the behaviour of White Marlin, i.e. Catamaran Ferry, ran some tests without finding the same as you have written two weeks ago.
At 695RPM, she runs at 24 kn or so and at first sight the speed curve seems normal to me, albeit without precise checks, as I would have done in a spreadsheet. Nor can I confirm the glacial yaw speed, as at 17 kn and 15° both rudders, I found a rather short radius of gyration, much less than 2 lengths. So, I think your dynamics files could have been corrupted/obsolete, or something like that, that is why I didn't look further down the investigation.
The White Marlin dynamics remained unchanged since 16/06/2013, RedJet4 since 2011, you can find these in the attachments.
These replacement act files should come into the following default folder
\Vstep\ShipSimExtremes\Projects\ShipSimExtremes\Data\Entities\Dynamics
while the bdg files destinations are, respectively:
for the White Marlin : \Vstep\ShipSimExtremes\Projects\ShipSimExtremes\Data\Entities\Ships\CatamaranFerry
for the RedJet4 :
\Vstep\ShipSimExtremes\Projects\ShipSimExtremes\Data\Entities\Ships\RedJet4
Eventually, if you disagree with the parameters, because you have real data or manoeuvring specifications, I would really appreciate if you published here the values/data, I thank you for that in advance.
Regards,
Luc