How many possibilities to get Type XXVIII?

[Fortune]

Hi,
I'm new to this really informative forum. So "Hi everybody"!

I've a few questions to the U-Boat Missions Add-on.
Starting my career in 1943 with a Type IX based at Penang,
the Type XVIII was offered to me in the beginning of '44.
But I declined it, because I didn't want to make my Patrols until May '45 with this boat.
So my Question is: Will the Type XVIII be offered to me a second time?

And a second one: Can you commend me some smaller mods for SH4 1.5.
Can't use Trigger Maru Overhauled due to localization problems.
Stock SH4 1.5 is way to easy(think I sunk more than 5 King George V Battleships, without really getting depthcharged by destroyers while I've been in the middle of the Taskforce), the destroyers are not aggressive enough and stop using ASDIC when my boat is below 70m?

Thanks in advance!


*Edit*: Type correction ...