I'm just getting back into bicycling since the mid 80's and picked up this Gavin Solo. It's pretty light and smooth riding. I'm 5'9" so I ordered a 54cm frame but I have the seat all the way back and I still feel a tiny bit cramped. I'm guessing I could swap out the stem but I'm new to road bikes. The stock stem is: "Tec9 25.4 60mm 0 degree Silver Alloy". I don't want to get the wrong size so if someone could give me an idea that would be great.