I like the DC Fan holder.
Transporting my Thing-O-Matic often I choose a very wide and long fan instead,
so it would never break of. (40x50 instead of 40x40 and 32mm thick with 2 fans and 2 motors)
Mine also uses a very strange bolt-size of M3.5 .
This required a redesign.
I am using 2 flat pieces on either end of the fan
instead of housing this large thing inside the DC fan holder.
My clamp-arm is not parallel to the wood but starting at 4mm and ending at 5.
This way it will clamp more securely and with more force.
To still attach it easily I tapered the arm by 2mm
(and the bolt holes by my usual 1mm).
The arm is also not as long as the fan.
With the fan 10mm wider, the arm would get in the way of the Z-endstop.
Thus it ends 15mm short of the back wall.