Double Gang Switch Plate Extension

Needed to cover a gap in the paneling left by the previous homeowner, so I designed and printed this real quick. Figured I'd offer it up in case anyone has the same problem.

Outer dimensions are 135 mm wide and 125 mm tall, which is about 20 mm wider than my switch plate cover and 10 mm taller. It's 2mm thick.

I printed mine with 2 walls and 10% infill, but I have no idea what would be ideal.