Hi, welcome to the forum, but why can't you check it at each angle, say, one-degree?

Maybe use a Spreadsheet to calculate each degree. Once you have the result for one-degree, just copy the Cell(s) and change the angle to two-degrees. Make as many calculation Cell(s) copies as the included swing-angle requires.

You could of course automate the process within the Spreadsheet if you are familiar enough with the Spreadsheet functions. That would require an advanced knowledge of the Spreadsheet, but just copying single Cells is an easier approach.

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I can't recall ever having done anything with pendulums, but wouldn't the max stress be at Vertical which I assume is at max acceleration and centripetal?

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