I just don't know that Hong Kong will keep a trident healthy in the long-term. Is there anybody who has successfully kept them and they stayed semi-evergreen, like Chinese elms in many cases? Winter averages in Hong Kong are similar to North Central Florida, and I know there has been some success with trident maple in North Central Florida. The difference is, I am thinking there are going to be a lot fewer hours below 45F(chill hours) in Hong Kong than in N Cen. Fl, despite similar averages.
Try it outside for a few years, and if that one does not make it, get another one and keep it in a refrigerator from December through February. As long as the roots stay evenly moist while in the refrigerator, it will do very well for you that way. I know, I did it for years when I lived in Orlando.