How can I figure out what size stems will be ok with my bike? I currently ride a 54cm, will a 90mm stem be too short?

how are people riding those stems that are short like stubs..?

oh, that makes more sense. it's a matter of feel, i guess. 90mm will put you more upright. longer will stretch you out. but there's no way we can tell you what will feel best for you. what do you have now, how do you feel on it, and how would you like to feel differently, if you do? these are things to ask yourself to figure it out. personally, i can run anything form 105 to 130, it's just a different feel each way.