The Mk2 was quite adequate, the extra sleeve made the most measurable difference, to the extent that on one 'maintenance' inspection I discovered a spider had silked up the weak kiddies fan and I hadn't noticed any difference.
It was a going cheap solar light, then I discovered that the sensor wouldn't fit in the luminaire, and the solar panel wasn't strong enough to turn the fan.
So I inverted the luminaire 'cage' to give some radiation protection and outer convection to the tube 'body' which became the container for the sensor.
Much testing with thermometers and positioning and housing showed that in STRONG full Sun it 'suffered' approx, 0.8C
So I literally wrapped a baked bean tin around it (temporary test !) and it was perfect
So the tin was replaced by the cheap ss BBQ grill, then when I was 'recycling' a dead PC I upgraded the fan (but had to buy a decent solar panel) ... and so on.
The beauty of the Stainless Steel is that it reflects everything, stays clean, and is slightly better on the eye for Lady beteljuice.
Downside (not for me - I work cabled) is that you would have to solder a wire aerial tail that came out externally to work wirelessly.
It was a couple of years later I realised that I hadn't quite copied a near perfect existing design (Assman psychrometer)
Just in case there are any believers out there - the first picture is a pastiche that I create during a looooong argument on sensor siting (for joe public) on another forum.