I copied and pasted this from the Perfectflite StratoLogger SL100 manual pdf.
Hopefully the row spacing doesn't "blow-up" once I post it.
It's not MissileWorks, but it should reflect the same pressure issue.
Edit: I just now looked, it did reformat... I don't feel like redoing the spacing, but you should be able to down load the manual at their website.
http://www.perfectflite.com/Download.html
Static Pressure Sampling Holes
You must drill one or more clean-edged holes in the airframe
into the avionics bay to allow outside air pressure to be
sampled by the altimeter (see table below for recommended
sizes). These holes should be as far away from the nosecone
shoulder and other body tube irregularities as possible (at
least 4 to 5 times the body tube diameter or more) to minimize
pressure disturbances being created by turbulent airflow over
the body tube. Sand the area around the hole as necessary to
eliminate flashing or raised edges. Best performance will be
achieved by using four smaller holes distributed at 90 degree
intervals around the airframe’s circumference instead of a
single larger hole. When using four holes, each hole should be
½ the size of a single hole as noted in the table. This will
minimize the pressure variations due to wind currents
perpendicular to the rocket’s direction of travel.
With any high performance rocket, pay particular attention
to the size and placement of the holes – do not make them
too large or too far forward! If your rocket has an irregular
nosecone (e.g. Honest John, Nike Smoke) you should move
the holes even further back.
AvBay AvBay Single Port Four Port
Diameter Length Hole Size Hole Size
1.6” 6” .032” .020” (small pinholes)
2.1” 6” .048” .025”
3.0” 8” .113” .057”
3.0” 12” .170” .085”
3.9” 8” .202” .101”
3.9” 12” .302” .151”
5.5” 12” — .286”
7.5” 12” — .5”
Single Port, hole size = Diameter * Diameter * Length * 0.0016
Four Ports, each hole = Diameter * Diameter * Length * 0.0008