Masonry bearing for windows of 6 cm

Yes, I can definitely understand that. I will let you take part in my project. I also find it nice to be able to share it. I wasn’t even aware of that at all. That makes me all the more happy.

I also think it's nice to be able to share it / allowed to share it.

We are glad about that. However, there are seriously quite often people here who are afraid that someone will steal their dream house idea if they lift the lid of the cooking pot by a second millimeter and/or think: that they are secretly copying the plan for their house here is less noticeable piece by piece. For those giving advice, however, this is frustrating: being questioned, not being able to "in return" share the excitement with the builders, and having to painstakingly remember the connections between the puzzle pieces.

Our architect planned 5 cm on each side for us. The masons said that is very much and usual would be 3-4 cm...

The bricklayers may not care, 5 or 6 cm is more of a challenging measurement for the window builders here.

Maybe something can still be gained when bricklaying. Possibly about 3 cm on each side so that you end up with 2 cm per side.

Where should the installation level be, especially where are the guide rails of the roller shutters located?