It happened. I'd like to post a photo of it, but it is too graphic and horrendous to show in public, so I'll offer an illustration and narration of what happened.
After careful drilling of all the holes with official plastic drill bits, I declared success! No cracks, no spider webs.. perfect round holes that even a CNC machine would be proud if, if they had feelings.
Then came time to tap 6-32 the holes in the rollbar. All of the holes were cleco'd (#40 holes; then final-drilled #36). I removed one, top-center/left-side. Put my 6-32 tap in and started turning by hand. The plastic was no match for it.. nice threads in the plastic. Then the tap contacted the metal rollbar. I suppose there wasn't enough pressure on the tap, as it had a hard time getting its teeth into the metal. Meanwhile, as the tap turned, the gap between the plastic and rollbar grew bigger and bigger. SNAP!
Being a wishful thinker, gee, it sounded like a cleco had snapped into place.. but then after I looked at the window on a slight angle, I see it had cracked. Beginning at the hole next to the one I was working on, extending backwards about 3 inches.
- stop-drill it. Use tank sealer on the crack & hole to prevent leaks
- Same, but don't seal the window to the turtle skin and eventually replace the window
- Toss the window and start over now ($400).
- Have a beer and pretend like this didn't really happen.
Note: the crack is above the rollbar's brace to the baggage bulkhead. So its not visible from the interior.