I like the little fan mount, cool idea. You could probably even get 2 of them on there and then cover the entire heat sink. Do you have a laser thermometer? Would be interesting to see what the temp difference is on the heat sink beneath the fan and on the sides.
Yes, I do have one of those.
temperatures:
Room: 30 degr C
Heatsink side: 40 degr C
Fan top: 41 degr C
Heatsink under fan: 61 degr C
Room temperature is pretty high because of outside temperature being 34 degr C here today.