DaMoshe wrote:
“There’s a big issue with the 7:00 early Shabbos minyanim. If you’re going to daven Kabbalas Shabbos before shkiah, you need to daven Mincha before plag. Plag today in Brooklyn is 6:22, so Mincha starting at 6:10 or so should work.”
Actually davening at 7:00 is much better than davening at 6:10. The reason is that by davening at 7:00, you are davening mincha before the Magen Avraham’s plag and maariv after the magen avraham’s plag, so there’s no issue of a tarti disasri. If you daven at 6:10, it means that you are davening Maariv before the Magen Avraham’s plag. The Mishna Berurah isn’t machria which plag is lihalacha. As such, by davening Maariv before the Magen Avraham’s plag you are making tens of (safek) brachos livatala. It is better not to daven at all than to daven Maariv before the Magen Avraham’s plag, unless you are a Granik.