When sirtut detracts

ב׳׳ה

The reason given for sirtut is to meyasher the ksav and for yofi haksiva and halacha le'Moshe etc.

In the following two cases it appears that the sirtut may hinder the ksav rather than help it, and was wondering your thoughts.

First case is the asvan ravravan, the large letters. The letters are not written on the sirtut itself, but with the sirtut disecting the letter in half. This can be easily discernible at a glance and gives the apearance of the letter cut in half by the sirtut. In addition, when writting a large letter since the sirtut, because there is a larger amount of ink and it is right in the middle of the letter, the ink tends to bleed more into the sirtut, making it harder to write properly. Perhaps this is a narisha svara but it would make more sense to rub out the sirtut in before writing this letter were it not for the divrei kabala that it needs to be there...

Example of where the sirtut is easily visible.

Second case is where you need to write a letter that intersects the vertical sirtut, like the head of a lamed. It often ruins the head of the lamed if written directly on it and forces you to lengthen the head, or otherwise fix it in another way that you would not need to, but not for the sirtut.

Example of where the sirtut 'ruined' the head of a lamed that and forced a correction afterwards:

I'm still a student of sofrus so will be greatful for לדעתכם היותר רחבים ונעימים בתחום. Perhaps you might shed light on a sevara why the sirtut is benificial here in any case, or any halachic works that might deal with this particular hinderance in ksav.

Thanks in advance.