I'm running with Imperial settings myself, and here's what I've found:
1. Torpedo running depth settings
On Imperial, the torpedo 'depth' meter operates in FEET, and does appear to work correctly. However,
many of the ship 'draft' values listed in both the in-game and in-manual recognition manuals are wildly inaccurate. I've verified this with extensive testing. I've also heard it stated that the game models torpedos running 10-15ft deeper than you actually set up until mid-1943 to reflect real-world problems with the depth calibrations. I haven't verified that with my own testing yet, though.
2. Mast height
This is definitely still screwed up on Imperial as of patch 1.2 -- supposedly it's on their list of things to fix for the next patch. Luckily the wonderful modders here have done some amazing work to correct the problem in the meantime. I use CapnScurvy's "Imperial Range Correction" mod on top of RFB 1.28 and have found my accuracy at range much improved. Highly recommend it. You can check it out, here:
http://www.subsim.com/radioroom/show...imperial+range
3. Distance (Stadiameter/Sonar)
I'm fairly certain that as long as you have the correct mast height, the stadimeter will then show you the correct range in
yards. As for the sonar, from the
very limited testing I've done it seems that the sonar man correctly reports ranges in
yards when Imperial is enabled, but the visual dial readout of the sonar still reports ranges in
meters! (Confusing, huh? Improving the sonar/hydrophone station usability is on the list for the 1.3 patch as well...)
Anyway, hope that helps a bit. Good luck!
nomad_delta