Welcome to Android Central! I'm not an authority on this yet, because I'm still waiting for my 6P. But I can tell you that my ASUS Zenfone 2 is almost exactly the same width as the 6P (77.2 vs 77.8 mm), and I can use it one-handed without difficulty. I have to shift the phone a little when reaching for the far left corners, but it's easy if I support the bottom with my pinky. I would consider my hands to be medium-sized as well (I use size 7 1/2 gloves in the hospital).