I widen the beam holes on the outer foam box. Now all the holes are ~ 0.75" in diameter.
We are concerned about the scattering on the insulation, so we decided to increase the holes' size.
I used a heat gun to heat up a steel rod to melt the foam panel.
As the insulation box was opened, I checked for scattering light inside the box. I did not see any scattering ligth except
on the ACAV inner insulation opening.
Also, there is a little scattering light at RCAV's insulation cap, so I measured the beat noise when I opened RCAV's inner cap.
There is no significant change, see fig 1. The trace with higher noise was taken when I opened the cap, probably because of too few average.
The scattering on RCAV cap might be negligible for now.