What is the amperage draw of the parasitic drain? It's not uncommon to have a few milliamps of current draw through the voltage regulator. If you've got much more than 1/10 amp (100 MA) that's too much. It would take several weeks to draw the battery down enough to give a starting problem with the tiny parasitic drain of the voltage regulator. Until you get a measurement of parasitic current draw, not voltage, this discussion is meaningless.
Jerry

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