Good job there! it works on my fiji cards. But you say only 4GB cards, so AMD 3GB cards are out of the game? I thought 144,5 had been carefully chosen precisely to raise the memory usage significantly but still allow 3GB cards to mine.
edit: rephrase
I was not aware of AMD 3G GPUs ... well ... they could work, just not tested it ^^
I just got news that AMD GCN 1 Tahiti cards generally work, just put this file
https://drive.google.com/open?id=1pN-zUv3pvJvrsETFbQ-8j_3gxercIObV into same directory as the other ones

It works with this kernel on 7970 and 280x. Good job again!