To be honest Steve for every good one there are many that don't make the mark
I don't really have any magic formular I'm afraid
I think its a case of trying to get square on to your subject, so that everything that you want in focus is as near as possible on the same level and also use as high an F stop as possible to maximise DOF.
In the case of the PBF they seem to hold their wings open very flat so that makes life a bit easier, with the Brown Argus that I was shooting today for instance, they would only bask with the wings at an angle, and so a portion of the wings is OOF even with a high Fstop.
Not much help I'm afraid, but there it is
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