I checked with Cessna several years ago about the strap over the windshield, as I had to replace one on my 337E. I was told that the problem was that over 180kts, there is a negative wind load (or suction) generated over the windsheild, that makes it want to pop out.
Therein the STC was for a half circle at the top of the windshield to hold it in. This was even if you had a thicker windhshield.
I opted not to go through with it due to the hassle.
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