Mark AJ6CU has made a 3D template for a fan cowling for your µBITx. The 3D template for the fan shroud can be found on thingiverse here:
It basically bolts onto the 80mm fan at the rear of the case (you might recognize the “tan” of a Noctua fan — much quieter than the one supplied). It sits on the uBitx motherboard with two slots straddling the heat sinks.
Marks notes that he has not powered on his µBITx yet, but suspects it will keep things nice and cool even in digital modes. This was designed with Fusion 360. There have been several other suggestions for adding ducts for cooling some of the hotter spots in our radios.
I was inspired in this effort by the work by another cooling shroud for the “shorter” of Sunil’s cases. See: