Hi John...

The side string is perfectly Ok... As long as the middle string is perfectly centered.

Even a slight slip will disturb the side strings too much to have an useable indication. And it is very unlikely that you enter a stall by chance while flying straight with a perfectly centered string.

The electronic instrument seems to be much less sensitive to that: Presently I'm using the pitot + static of the fuselage, plus the centered pressure port under the nose and it is Ok... I should check by using the antenna pressure to confirm...