VII/ VIIC surface depth is too far out of the water

[Average Joe]

I'm having trouble with the VII/VIIC sub running at the proper surface depth. It's running higher than normal; the depth gauge says 3m.

A stock install of SH3 shows the VIIC surface depth at about 5m.

The .cfg file is correct for surface depth (SurfaceDepth=5.8;meters). I've changed this number to see if it helped, to 7.8m, but the sub still rides on the surface at 3m.

Can anyone tell me what other file(s) I may have messed-up, that caused the sub to ride so far out of the water?

I have a stock SH3 install too (no mods) and could fix this problem with stock files, if I knew what files to copy over to my modded version of SH3. Any idea as to which file(s) might fix this?

p.s. I thought the depth gauge might be wrong. It's not because I've checked the VIIC with camera-view enabled, and it is riding way too high out of the water. Props are out of the water half the time, even in calm seas.