When I wrote last post I hoped to finish it in a few days... and then got distracted by other things for months. Still, now that I have some time again, I dug the files out in order to finish it.
I still have to make some final improvements to the model and then texture it (which might take a while since I'm pretty much a noob at UV mapping) but I did a test import into game and it worked pretty well in most regards: it shows up in game, sails, fights, explodes and sinks no problem. Because of lack of Hotchkiss 3pdr I used single 2pdr on front deck and Oerlikons for AA mounts.
Now one thing I couldn't figure out is how to make a working ASW weapon. I made a W01 (asw) slot where Fairmile historically mounted an Y-gun and as far as I can tell, I configured everything identical as it is in Japanese Akizuki and Sub Chaser dat-format ships, yet those ships show up in game with ASW weapons while my Fairmile has an empty spot there.
I got Y-gun to show up when I put it in M01 (main armament) node but it refused to fire. Anything I try to assign to W01 node just doesn't show up.
EDIT: Done some more experiments with W01 slot. Well... any ASW weapon I put there works now... with exception of Y-Gun. Sigh.
SH5 with TWoS has 4 Y-Guns in game files: two .gr2 (YGun, YGun_Mk9), which show black on a .dat ship (don't mind the ship ugly texture for now, it's a placeholder)
An SH4 version which shows up like this and refuses to fire:
And SH3 version which doesn't show up at all.
I have no idea why SH3 K-Gun and DC rack work in SH5 and Y-gun doesn't. Tested it with other ships (like Japanese destroyers) and results are the same.