I would like to suggest giving the 3,7 cm Flaks also the Navys Pzgr. L’Spur as allready found on boats.
The Kriegsmarine had the 3,7 cm Flaks such as Flak 36, 37 and 43 not only on the boats themself, but also for costal defence and some Self propelled ones as well.
While there is no fixed documentation who all got the Navys Pzgr, giving it also to the Heeres vehicles such as the Sd.Kfz. 6/2, Ostwind, Ostwind II, Flakpanzer 341 and all that have yet to come wouldnt be unhistorical, as there where such halftracks also armed, however the tanks and halftrackt in game are depicted as from the Wehrmacht.
It would offer the lower vehicles such as the Sd.Kfz. 6/2 an stronger alternative to the Pzgr. 18 L’Spur as well as an intermediate Ap round befor the H-Pzgr L’Spur for higher Br Tanks such as the above mentioned.
Its an Apcbc 0,7 kg 815 m/s Solid shot. It would trade after Armor effect for higher penetration, while also using a higher charge than the Pzgr. 18 L’Spur (which it also was available with).
German Artillery of World War Two
Hitler’s Navy: The Kriegsmarine in World War II
Kriegsmarine Coastal Forces