First of all, I want to congratulate rowi58 on his excellent work to fix the FuMO-391 radar for the type-XXI U-boat. And thanks for sharing it !!!
After having read the post by JScones, it seems that the fix provided by rowi58 is almost perfect.
It is very difficult to find information on the FuMo-391 radar, and the fix provided by rowi58 matches almost perfectly the data found in the reference provided by JScones. (and the data published in
http://www.uboataces.com/radar.shtml)
However I have found additional details on the FuMO-391 radar on the book "The U-boat. The evolution and technical history of German submarines" by Eberhard Rossler:
"At the end of the war, two items of active detection equipment that could be used at periscope depth were still in the test stage. These were the German 9cm FuMO84 "Berlin II", which had a stern emitter in a presure-tight casing on an extensible mast, and the active surveillance apparatus for use against the aircraft, FuMO391 "Lessing" (2.4m wavelength) with an extensible vertical aerial. These were intended for new U-boats from the summer of 1945"
This reference confirms that the FuMO-391 was developed to be used also while at periscope depth (and therefore the top of the Schnorchel seems a feasible and good place to install it). However this last reference states also that the FuMO-391 was still in the test stage at the end of the war.
In any case, taking into account the two references available, it seems that the mod-fix developed by rowi58 is a good fix for the bug present in SH3 with the FuMO-391 radar. In my opinion this fix should be included in the major mods that feature the type-XXI U-boat.
Grey Wolves X modders: can you include this fix in your mod??
Txema