Was my question understandable or do i need to reformulate?
or is there no one who knows if its possible?
Even a "no its not possible" would help, so i could stop looking for a way to do this
Create a sketch of the hatch.
Extrude a surface-extrude from that sketch, make sure it goes through (or at least touches) the end surface.
Use the "intersection" method. Select the "G" shape as your first, and all the surfaces as your second.
Sit back, get a drink, and hope your computer doesn't crash. This is going to take a long time.