Not sure what C and D nodes are for, didnt SH3 have Huff Duff so maybe that is D. They aren't used in any ships I've looked at. They are usually on or near the bridge. They should work as dummy nodes for radar if you specify C01 to have the right type in the .sns file. If this approach isn't working, I don't know why, but I've added R01 nodes to all the escorts that are missing them.
In relation to your wish to get fire control radars to fire guns through fog, I don't think they are in game as a radar "type". I have seen ships fire through fog at targets that are in visual range of other friendlies. So they can blind fire - sort of... at the moment, I'm not looking at this though.
In goblin editor it states for some sensor values that if 0 the value is read from the sim.cfg. So the opposite is true if not 0 the value is read from the AI_sensors.sim instead. It does not state this for surface area detected, but it might still do this.
Guns_radars just seems to have the director model for the fletcher, it has no sensor values. It is just a model. So are the other radar models in that file. They do nothing for gameplay.
The ships I have modded seem to detect me now fine. A Town class with a type271 detected me in thick fog on calm seas at around 6km. It turned toward at full speed etc then attacked when in range.
The various radar nodes could be used to attach air search and sea search to the same ship, though I don't see the point in this at the moment, as the radars (even the surface searchers) all work up to high altitude and have the elevation and traverse to detect anything large enough. Plus only surface search is important to gameplay, but it could be looked at later.
I used R01 for the director on the fletcher and cloned it to R02 to add SC, SG etc as war progresses. Seems to work.
With regards to wavelengths I ask because as I understood it radar wavelengths determine target size for detection. Most of the centimetrics in the game are set to detect 0.3 by default and in goblin editor the units are supposedly m2 (that what it says anyway). Centimetric radars were approx 100mm wavelength and 10cm x 10cm = 0.01 m2 i.e many times more sensitive than the 0.3m2 listed.
I can upload the escorts from my sea folder for testing purposes. Also the AI_sensors etc would be needed. I basically went through all the radars listed and found their wavelengths on the net / books etc then converted that to surface area as above and re-entered the new values. Not touched range or anything else. Its just my sea folder contains a whole load of other mods, like my new Town Class that I'm working on, removed ship reflections etc buffed DC loadouts and other stuff.
Some aircraft do have radar, the Sunderland, the Catalina and the Heavy bomber all have R01 nodes and corresponding ASV radars in their sns files, and I'm pretty sure I didnt put that in (maybe I did though - and forgot!). The Swordfish, the Buccaneer and perhaps 1 or 2 other could have it added. The swordfish used early ASV to detect bismarck in 41, and the Buccaneer in game is a effectively a proxy for the Avenger which also carried ASV later on.
Thing is making these changes will make the game seriously more difficult in 41 - 43. I haven't got near a convoy for a long time now in my 43 campaign... its horrific!
http://www.gamefront.com/files/23404686/Escorts.zip
contains all sorts, not JSGME ready, this is all WIP at the moment, you can probably enable it easy enough though.