@mfalkvidd Didn't think of that... I can try changing the delay() to a sleep() and see how much that impacts the temperature...
(But I still am open to ideas to help insulate the sensor, and am now also wondering whether creating extra vent holes on both sides of the rf-nano might be a good idea, even if it means more dust can come in as well...)
In my sketches I had to define the below for the built in radio to even work:
#define MY_RF24_CE_PIN 10
#define MY_RF24_CS_PIN 9
Also, I have rf-nano's from 2 sources, the one I got from the first source (don't recall where it was from) doesn't send anything at all, according to the RasPi gateway*), the other 4 (from the 2nd source) just worked
*) the radio initializes just fine, the gateway doesn't see any messages from it at all!...
Putting the graphs next to eachother, the graphs looked similar, and after guesstimating the difference and applying that to the sensor as a correction in Domoticz, the graphs are overlapping sufficiently to explain the differences by the difference in location (one is in the center at ~1.7m height, the other on a shelf in a corner at ~2m height) and standard deviation...
I'll keep it like this for a while and will reevaluate at a week's interval.
FWIW I am actually doing the basic oversampling, while doing the timed single samples.
If it remains an issue, I could modify the code to start the sensor with reduced oversampling/accuracy setting, but for now it looks good (enough)...
Sorry for the lack of response, life's been crazy... Thanks for the reply, I have since recompiled, but need to make some add'l changes to the sensor sketches, so I want to do all of that at once before I deploy to the new channel... 
@mfalkvidd Just a quick update...
Been extremely busy, so not a lot of time, but when I run the recompiled version (channel 109) gateway and use the existing - known good - sensor sketches with the channel 109 macro declaration included, it doesn't connect at all.
When I run the "old" version of the gateway and the same sensor sketches with channel 109 commented out, it just-works...
More testing and such due I guess! 