Well,
The canopy is drilled and the front installed and so far nary a hitch.
I never used the plexiglass bits I got from Brown Tool.
My technique:
Made the frame. I put in all the pilot holes, spacing, etc. before assembly and up drilled to #40. (The parts were replacement parts for a 6 and had no prepunched holes.)
Installed, cut, fitted and clamped the canopy on gently with soft clamps.
Back drilled the plexiglass with a homemade #40 bit made using instructions by
www.plasticmag.com and Dan H. Its easy to get "dead on" the frame hole if you do it carefully and check the hole location a couple of times during the slow drill. I clecoed each hole as I did it to keep alignment. Chamfer both sides of canopy with a zero flute c-sink.
Countersunk with 110 degree 3-flute in a microstop while the canopy is installed and clecoed and the frame holes help keep the sink from wandering around. The edge of the countersink was made just slightly wider than the #6 dimple or the #6 Tinneman washers.
By this time I could no longer make a decision between 5/32 or 3/16 up drilling so I took a new 11/64 bit and converted it to plexiglass configuration and enlarged the canopy holes.
Rechamfered the back side of the plexi and drilled up the frame to #25
All screws installed in the front and no cracks yet.
If I had known about it in time, I would have used the tapered drill reamer shown by the other members. Would have saved a lot of time.
I still believe 80 F+ temp is the key. I warmed the canopy carefully with a small electric heater under the canopy and a blanket over the top and monitored the temp closely
Dave A.
6A rebuild