On the trimmer line spool, it lists both .080 and .095 size string, one size per hole. By visual inspection the holes actually look to be different sizes. Am I supposed to use both sizes of trimmer line on the spool? Would that throw off the balance of the trimmer head? Lastly, if not, does that,both size indicators, just mean I can use either size line?

Yes This is showing you can use up to a .095 line.
Luck

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How do I restring the trimmer line on homelite 26ss