I have a LPL C7700MX / Omega 670MXL Dichroic enlarger (with colorhead). I use this solely for B&W-work and consider doing the following modification:
I intend to replace the cyan filter with an equally sized steel-plate on to which I have drilled a number of small holes. The total area of the holes is 1/8th of the area of the “non-drilled plate”. When I dial in “maximum cyan”, the plate covers the light-path completely and only 1/8th of the light pass through, which should equals stopping down 3 stops. Hence, I have made myself a ND-filter, continuously adjustable from 0 to 3 stops.

Is the idea presented above sound? Should I go for a few rather large holes, or many small holes? Are there any pitfalls that I have not considered (diffraction perhaps?)? Any other suggestions to implement a neutral density filter into my colorhead?

For reference, I have attached an picture depicting the filters in place (the cyan filter goes first in the light-path, i.e. is located most backwards in the filter-stack):