Front sensor mount and blower duct

For months I had been using a 18mm inductive sensor mount that mounted to the heatsink side of my extruder. It's a very common design and it worked pretty well. However, it was subject to some torsional forces applied by it's own cabling, which manifested itself in gradual error relative to level across the x-axis of the printer. I could overcome this by waiting until auto-leveling had completed, and then adjusting the right side of the bed up a half-turn using the thumbscrews. (~0.25mm)

I decided to make a more robust mount for my sensor, and chose the front-side for the location. This necessitated moving the blower over slightly and designing a new fan duct as well.

If you don't like ring-style ducts, you could simply cut or snap that part off. The duct is still aimed right at the nozzle.