As an aside and following on from EchoTango ..
In addition to the previous commentaries, consider that
(a) a significant concern with pitot static systems (which have already been through the certification process) relates to the consequences of disturbed flow (ie different to the calibration conditions) in the vicinity of the static source.
(b)a very significant part of the certification flight test process involves the determination of PEC data.
Such airflow problems can arise from ill-considered or tested modifications or other physical changes upstream of the sensing location including comparatively minor local damage in the vicinity of the static source.
It is very easy to generate quite significant instrument errors from these sorts of problems.