Nice one Rolf, looks like I've got some catching up to do. You have a nice setup there. Of course we will be expecting even better pix than before, no pressure ...
I've got a wee fan aimed at my secondary but haven't had the opportunity to test it's effectiveness yet. By the looks of yours mine may be inadequate, soon see. Easy enough to mod. I have at least 20 of them in various sizes and plenty more available. I have some so small you could mount them behind the spider easily and they would not extend outside the hub diameter. Give us a yell if you need any to play with.
Cheers
Brent