As soon as I receive the corsair h80 I will disassemble everything to change it, and I will take photos of the graphics card. The only problem was that I didn't have any black electrical tape left, so I used the green and yellow one. If not, the appearance is not something that worries me. I am not worried that the tape could be damaged by temperature since those temperatures would be very well tolerated and you would be surprised at the temperature that materials like cardboard can withstand. A while ago I built a DIY projector and used a 400w lamp as a light source. Imagine the heat that generated. All the ventilation holes of the case were protected with cardboard casings so that not much light came out, and there were zero problems. In the worst case, I suppose there could be fireproof cardboard with which the structure for the graphics card fans could be made, although seeing the results, for the moment I will leave it as it is.
No, I know, household materials can work wonders... xD
If it can last, it can last you until the end of your days, but it's not something you can be sure of. It's about giving consistency and security to the matter. With a couple of solid materials you put it together and forget about it, with electrical tape and cardboard you will surely be checking it from time to time.
But I reiterate: if it works for you and you see it as consistent, excellent. If everything we discuss will be in favor of solidifying and improving the mod as much as possible 
Regards