Many thanks for your kind words guys
Before the exhaust smoke of snorkel, there was an important thing missing!
None of OM snorkels were virtually active
because no tube linked from snorkel to engine room! (And no snorkel support on conning tower)
Now this is present and effective in 1944/01/01 for all U-Boats snorkel equiped.
Here the VIIC in early 44:
More to come ...