Hi everyone,
The sloop of war you are comparing her to is the Brig from PotC right? That brig looks like it is based on the Russian Brig Mercury 1819 as I found some models on this website: http://www.shipmodel.ru/shipmodels.htm
Among the fine models on this site you may notice the 32 gun frigate Russia which bears a strong resemblance to one of the frigates in PotC too, even the PotBS Valiant (Ingermanland) is here as well.
The brig that is based on the Mercury should be larger than it is in game since its a larger vessel (stated as Length 96.7ft x Beam 31.5ft), it also apparently displaces over 400 tons while the Neptunus is 188.5 tons (moulded). I have also noticed that the corvette is too small as well, the Neptunus is 79ft 8inches between perpendiculars and 23ft extreme beam and the in game corvette is not much larger but has a lot of guns so it must be a model based on a larger ship possibly a frigate.
I have a couple of books by Howard Chapelle and in his book the Search for Speed Under Sail the Neptunus is to my surprise mentioned in it, even the original draught of her before Chapman altered it is present too. Here is a little of what is written:
The Neptunus displaced 188.5 tons (moulded). Her block coefficient was .42, midship coefficient .79 and her prismatic coefficient .55. The very low prismatic is due to her extraordinarily fine and long run, as well as to very easy buttock-bow lines forward, combined with a large immersed midsection.
Chapman states this vessel went 16knots. Varying estimates of the length of a nautical mile in 1720-30, however, made it probable that her real speed was about 13knots, modern measurement. Even so, her speed-length ratio would be abnormally high for a waterline length of 76ft 3in, since 13knots represents a ratio of about 1.49.
Now I don't claim to understand what all that means I just wanted to point out that the ship was an abnormally fast ship like the Peregrine galley for example, so maybe give her a decent speed and better than average handling (a little worse than a brig) since she is not a heavy or large ship. Also the rig I modeled on her is relatively modern with studding sail booms on the main and top mast yards as well as the gaff on the mainsail (gaffs appeared on frigates a lot later than they did on small ships).
The rudder is also another clue to a ships performance, as small rudders usually mean a fast vessel. Here is another example of a fast ship design:
http://americanhistory.si.edu/onthewater/collection/TR_318280.html
http://i980.photobucket.com/albums/ae282/jamesjn/Armed%20Schooner%20Berbice%201780/BerbiceRender01.png
http://i980.photobucket.com/albums/ae282/jamesjn/Armed%20Schooner%20Berbice%201780/BerbiceRender02.png
http://i980.photobucket.com/albums/ae282/jamesjn/Armed%20Schooner%20Berbice%201780/BerbiceRender03.png
Captain Hawks smuggler mod inspired me to model this as I wanted to replace the colonial schooner with a suitable ship (no offense to anyone I hope) I also have plans for a few more schooners, sloops and other small ships and will post about them once I have made more progress.
Cargo capacity is difficult to specify though, she wouldn't compete against a hauler but since she is a Privateer her main purpose is to capture ships as undamaged as possible to maintain the prizes value and would need a large crew to man said prizes. With this in mind she would need to feed this crew and also carry other provisions and stores as well as carry her armament effectively.
For the stats in game I do like what Rider supplied with the ship but the stats should be adjusted as people sail her especially with regard to the crew, cargo capacity and turning.
Regards,