Hi gosd,
How are you muzzleflashes going? If you look at the muzzleflashes in post #11 above, they are the stock fx_muzlflsh_s, used at the end of each gunstation where the type= one of the 25mm AA guns.
So at the end of the gunstation line in the destroyer's .xdp file, I put Muzzleflash="fx_muzlflsh_s", right after the ammo setting. However, as your effects xml also has fx_gunblast_s, you could try that on the v1 destroyer, and fx_muzlflsh_s on the v2 destroyer, and see which one is better. It is easy to modify the mission which Liquidchicken provides, by adding a destroyer as an additional unit. I have taken his mission, and created a small battlegroup, adding Suzuya, Mogami, and both types of generic destroyers, so as to test things.
Lots of flak!
. In one of the weapon xdps for one of the 25mm AA, the type="shell". To get flak bursts from that AA gun, the change in the weapon's xdp file reads Type="flak_gun". Liquidchicken made it a shell, so as to ease some of the burden on the video card. But if you system is up to it, making the weapon a flak shell certainly makes things intense when you approach the Imperial Japanese Navy...