Thanks for the link with the picture of the Zenoah stack spaceworm. I was planning on how to machine one up out of brass or aluminium, but could not figure out how to get the bolts in. The Zenoah one solved that with the half round recess's removed to take the bolts.
Also, the trumpet shaped flare does not need to be so pronounced.
Where I will be flying is often very dry and dusty, so I will likely fit a stainless screen to it. If I do it in brass, the stainless screen can be silver soldered to the intake.