Hello ten010, the mission I used is the one you uploaded in the thread, I have not yet tried to make a mission of my own.
I used TD 4.11.1 with SAS Modact 4 for the trial flight.
I have only added aircraft to the install, no other ships or any kind of take off mod that I am aware of.
I have 000_1956_Core_v13 installed as well as !SAS_Engine_Mod_4111m_v26, both I believe are the latest versions.
Here is a take off sequence from your mission:
In answer to one of your question, the aircraft is not exactly in the centre of the submarine.
Each time I try this the end is different but essentially the aircraft takes damage as it tries to launch to the side on take off.
Wind setting in the mission maybe?
Hope this helps.
Just for info, although I would think it not high on your to do list:
I added the M6A1 to my stationary planes mod and it it seems to be afflicted with a problem prevalent with a lot of sea planes, it stands up off the water surface.
Gorgeous submarine bye the way.
Wishing you all the very best, Pete.