I feel your pain. Transporting wine is a most difficult process these days. And how awful it would be to have to open a bottle of OpusOne at the gate to prove it wasn't kerosene for an inflight molitov cocktail! [Well, awful, unless I was standing behind you and volunteered to assist in the assessment of the contents.]

But you have identified the real issue: inconsistency from one airport to another, and often from one gate to another. I would suggest carrying no more than 3 bottles, and carefully wrapping and packing the other 3 in your check-in luggage. I did that on a recent trip back from Australia. I realize the checked bags will cause all sorts of shaking of the contents, but save them for the final days of the cruise. I wrap each bottle, first in newspaper, then insert them into a double plastic bag. I then wrap this bundle with a shirt, and place this into another plastic bag. Packed in the very centre of my bag, I have never in 20 years of such transport, had a broken bottle.