dokterd1... i'm sort like you and i left 54 when i was like 14 y/o... well the difference we have is that im talking about a 54x54 cms steel frame, versus the trek that who know how is doing to consider the frame sizing.

Eventually and probably people will tell you differently because everybody has different opinions, but as a top size you should be in a 56 right now. Now i have to translate this into modern frames ok? Now a days the measurements are so wacky that u have to buy a frame looking at the length of the bike, doesnt matter if the brand calls the bike medium, small or whatever size, always look at the VIRTUAL Length or effective length of the frame (if it is a compact or sloping geometry) with regular geometries u have to do the same, forget the seat tube size and go for the length of the frame. Frames nowadays tend to have short seat tubes and long top tubes on in other words modern bikes are longer.

Regarding stem probably the 10 cms one is too small, 11 cms might fit fine but who knows, I would start with an 11cms anyways.

Another advice, if you are looking for a new frame and u like one with sloping geometry, as i said before look for the effective length of the bike but if there is nothing in 56 for example go for the closest in the lower tear like for example 55 or 55.5. If you go over like 56.6 or 57 the frames tend to be too long in my opinion. If you are expecting to grow a few more cms i would bet to the next size if i was you. Lucky me and lucky my dad Ii stopped growing at 16 y/o.