Vanilla is the term used for the standard game when modding, kind of like standard ice cream, vanilla!... i return to the default clouds included in AC V1.8.1 (-> you call it vanilla?). Use the ppfilter "default bright" and "4_mid_clear" also default (rise the number of clouds in weather_ ini file. Not really satisfied with this sky and horizon colours. I know you could improve it ...
So your using one of the default filters as well? As soon as I get a chance to have a bash I'll get on it and implement an optional weather pack that helps those with fps losses. Out of curiosity are you losing fps using my filter hence why using the default bright one? If haven't tested, try using it with the default weather and clouds and see how you get on with frame rate. If so I can try and make it more graphics card friendly, just with the weather pack it's meant to be used with the filter and gets the best colours and lighting out of the weathers as I've edited them using that filter. If you let me know the reason you're using the other filter it it would help a lot. And I'll get on making the pack.
Many thanks.