You can always use one of these tricks to gain access to the fan settings, and sometimes a few more other options.
blocking a part of the fan might damage the chips behind the blocked part, this is the reason why almost 99% of the time it's the chip behind the fan motor that gets toasted, well using an air filter is not as bad as blocking the whole thing, but I would still be careful, it would be safer to actually set a static fan speed in my opinion.
Anyway thanks for following up, most people don't, gave you a merit for that.