Umark question.
 

What .dat file controls the Umark?

If your talking about that thing that shows where your sub is?
There is no dat file that controls it.
Edit the UMark.dds file to change it.

Download TMO. Copy the umark.dds from there to your game. Shazam! Umark gone!:D

If you've got photoshop and the nvidia .dds plugin for it. Just paint the alpha channel in it solid black so its completely transparent. Save format for that file would be DXT5 Interpolated alpha, no mip-maps.

The lowdown is this. I have a copy of SH4 with Opmonsun and the umark was removed. I like to play with it and I have added the umark back into the misc file but it's still not showing up. So I thought that perhaps it was controlled in a . dat file. Any ideas?

Uninstall Opmonsun.
Dig into it to find the modified UMark.dds file.
Delete it.
Reinstall Opmonsun.

Since the file is no longer in the mod, it won't overwrite the existing file, and the mark will appear in-game.

Here's the Stock SH4 Umark.dds file.
http://www.mediafire.com/file/bx965vkfcv3aa9c/UMark.dds