I settled on using the motherboard fan headers as it was the only way i could retain full functionality of my 1080, whilst being able to achieve the noise levels i wanted. I outlined what i did here as well as some of the drawbacks of doing so...
https://smallformfactor.net/forum/threads/zotac-gtx-1080-mini.1116/page-15#post-95247
Regarding the probe. How did you get it to stay where you wanted? Tape? Zip tie? I picked one up and I'm trying to get my mind around all aspects of this before I start taking things apart.