I have a dropper on my EX9 27.5 19.5/18.5 frame size. I love it, especially the Rock Shox post because it will lower to what ever height you want, others have presets that can be an issue. Probably what your buddy had. Typically you set post so the seat fully extended is where you ride at. Then lower from there. Matt, did you test ride a Large frame? I am 30-31 inseam and ride Med-Large Frames. my EX 9 is a ML size. But trek has typically more size options than most. Not just S, M, L, XL. But everybody is different. If you feel to cramped you can go with a longer stem. I had to on my EX9, front end was to light, was washing out, added about 10mm and got more weight over the tire.