The net scabbard should be drilled to allow water to escape. If that is not the case, they have either not drilled the bottom tip, or the scabbard has gotten clogged somehow. An extension will likely be necessary to drill it and you can drill it further forward, carefully through only the 3/16″ of glass. You also may be able to access it with a straight line drill or drill flexible extension, through the floor drain. You should be able to gauge the space at least by looking through the floor drain area. The space to hull is tight, and you will see that.
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