Glued laminated timber above window

[MBZV]

Had windows replaced in our Myresjöhus from 1976.
Now I see that the interior ceiling has "sagged" about 2cm in a room where we replaced what was probably a load-bearing window with an Elitfönster. The window has a width of 180cm. Therefore, I need to install a glued laminated beam but would prefer to place it on top of the roof trusses in the attic as I'm not too keen on tearing down the interior walls.
According to the Moelven calculation program, with the opening measurement and with the roof angle of 15 degrees, I should have a glued laminated beam of 66x315mm. Does the same measurement apply if you place it in the attic?

 

[etiol]

Hi ...
How long does the beam need to be ..??
How many rafters need to be put up ??
Can you insert a picture,
Of what it looks like up there where you intend to place the beam
and down on the ceiling..
Eti...