I know this will sound crazy, but one of the things that helped me was using a battery grip on my camera, yes it adds about 230grams to the overall weight and yes weight is a big issue for me, but it balances so much better in my hands now that I don't hardly notice the extra weight.
If you think about it you have an 800 gram camera with a 1200 gram lens on the front, so it will be a bit nose heavy, this can be wearing and hard to hold for some, myself included, but adding weight to the camera itself brings the balance point closer too you so that in the classic grip of one hand cupped under the base of the lens and the other on the hand grip of the camera it balances and feels steadier in your hands.
It's work popping into a local dealer and trying one out with a couple of batteries in it to see if it works for you.