I've brought back a 1.75l of Grey Goose, bought in LAX and brought back in a clear sealed bag with receipt inside etc.) twice from LAX in the last year and successfully connected through T5, and also T3 (?) to T5 with it.

The only problem I had is that they have a specific security arrangement with sealed bags and the first time this didn't happen causing me a wait of an hour once (lovely end to my first First !) when they wanted to X-ray it (that size doesn't fit the X-ray machine) and then the brains engaged and a manual search and swab did the trick.

I suspect you need a better rouse than that sadly