That is what the GX4 looks like with the Hogue Handall Beavertail for P365XL with both the Taurus 13rd Mag and the Lakeline Pinky Extension: I Have not Bought the Lakeline extension yet, I do have the Hogue Grip and like it with the 13 rnd, and yes it is a good fit ,
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So far my strong preference is the Taurus 13rd Mag.