R9 Fury memory OC for eth

[Zucca]

I am mining eth with a Asus Strix R9 Fury 4gb@Samsung .
It gets ~29mh/s in eth solo and ~28.2mh/s in dual mode.
If I try to change memory clock with MA from 500 to 525, it seems to work, but when I click apply, it goes back to 500.
I tried checking the box "extend official overclocking limits" and it didn't help.

Is it possible to overclock the memory of the video card?