Herb, I will enlarge the holes a bit. Since the top is pegboard the counter sink idea won't work. Had I built something like your impressive box, with a thicker top, I'd do that. Thanks for the suggestion.
DownDraft Box
Here is a downdraft box I just completed today for sanding with my ROS. I used the Rockler plan pdf. that I downloaded off their site .
http://go.rockler.com/tech/25077-Down-Draft-Ezplan2.pdf
I had a part of a sheet of prefinished 1/2"birch plywood I had bought and used for drawer sides. The box is pretty simple to build. I made my own perforated top pieces. I had built one years ago off the same plan, but they had small 1/2" holes and it cut the air flow so much ,I decided to make the holes 1' dia. spaced 1/4" apart.
I tried several drill bits to drill the holes and settled on the spade bit with the scoring ears on it.
I tried a Forstner type bit, and it cut OK from both sides, but it was slower, plugged up,was harder to exactly follow the pilot hole as the pilot point was so short.
The 2 auger type bits were the best cutters, but the threaded pilots would lift the material off table table fast.
The spade bit has a long tapered pilot that centers from both sides easily and the spurs do a good job of scoring the outside cut. I never would have guessed it ,but it worked best for drilling from both sides.
It took the longest to drill and finish all 278 holes.
The pictures tell the story.
Herb
http://go.rockler.com/tech/25077-Down-Draft-Ezplan2.pdf
I had a part of a sheet of prefinished 1/2"birch plywood I had bought and used for drawer sides. The box is pretty simple to build. I made my own perforated top pieces. I had built one years ago off the same plan, but they had small 1/2" holes and it cut the air flow so much ,I decided to make the holes 1' dia. spaced 1/4" apart.
I tried several drill bits to drill the holes and settled on the spade bit with the scoring ears on it.
I tried a Forstner type bit, and it cut OK from both sides, but it was slower, plugged up,was harder to exactly follow the pilot hole as the pilot point was so short.
The 2 auger type bits were the best cutters, but the threaded pilots would lift the material off table table fast.
The spade bit has a long tapered pilot that centers from both sides easily and the spurs do a good job of scoring the outside cut. I never would have guessed it ,but it worked best for drilling from both sides.
It took the longest to drill and finish all 278 holes.
The pictures tell the story.
Herb
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Sometimes you just have to re-purpose the early designs... 
https://3.bp.blogspot.com/-ACoiP8I1...4qg5r9yrSKo0CXS3dB1gCLcBGAs/s1600/OACGBox.gif
https://3.bp.blogspot.com/-ACoiP8I1...4qg5r9yrSKo0CXS3dB1gCLcBGAs/s1600/OACGBox.gif
LMAO, Fat cat.Sometimes you just have to re-purpose the early designs...
https://3.bp.blogspot.com/-ACoiP8I1...4qg5r9yrSKo0CXS3dB1gCLcBGAs/s1600/OACGBox.gif
Herb
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