This is really just an extra arm to mount a BLTouch sensor added to Drax's excellent Hemera XS 5015 Fan duct, with minor modifications to adjust the duct outlets to match the older Hemera (the XS is shorter).  I also added a small slot for the ridge on the 5015 fan, although that's more personal taste than necessary.

The BLTouch is further away from the nozzle than might be ideal (it's about 60mm in the X, 14mm in the Y), but other than making sure the print is sturdy (higher % infill) it seems to be fine.  Note that you could put the BLTouch connector on the Hemera side if you need to keep the wires clear from the edge of the printer.  It's easier to connect if the wires are facing away from the motor.

In the pictures the duct is printed in black PLA, it really should be PETG, ABS, nylon, etc. (although I suspect this roll of PLA is mislabeled, it requires 260C to print.  It might be PC, which would also be good).  I generally use PLA for development, at the moment this version seems to be working well (and it hasn't melted yet).

I've included a Fusion360 archive of… everything, including the Hemera, Hemera XS, fan duct, BLTouch, etc.  Basically Drax's archive with new stuff added.  Should be fairly complete.

The printer in the pictures is a “RadZ”, which is the second (third? Fourth?) significant modification to the M3D Promega large format printer.  “ShadowMega” was the first significant modification as I recall. It has very little left of the original Promega apart from the case, probably for the best.

Edit(s) 5/23/2023, v12

Played a bit with spacing, offset the BLTouch slightly to help with adjusting height. Modified, hopefully improved, the fan input.