Thanks Corsair, but I think my video card is too weak. I made a double install and the game's running fine when alone at sea. But I attacked a big convoy and the game then became really unplayable : incredibly slow and at times almost frozen. Using the freeview at one point even made my computer crash : not a simple CTD but a total reboot !
New boat textures, more details and accuracy to the eye (among tons of other things) makes bigger (and more numerous sometimes) texture files that my video card has some hard time dealing with. But it's the price to pay to play a better game. So, later for sure ! I'm not in a hurry to play GWX : to really appreciate the taste of caviar one day, one need to be used to eat potatoes first.

Don't people see here anything against IuB
at all, it's already an incredible improvement compared to the stock game. But I've been playing Silent Hunter since the very first issue (SH1), and I'm - sometimes - a kind of patient guy.
Except for this damned broken cables that are ruining my wonderful (and personalised by myself) skin from Fubar !
Here the arrival at Las Palmas, cables broken (not obvious, but trust me !) :