I also have large hands and my conclusion is that my typing performance depends on the position I'm in when typing (worst when I'm lying on my back, best when I sit straight) and on the time of the day (best when I'm fully awake, worst when I'm distracted or tired).
Ironically I mostly have the best performance when I watch the typed text rather than the virtual keyboard. On the computer I type with the 10 finger system, so I always just look at the text, but on the smartphone I just use the thumbs, but still it's better if I type blind. I think this is, because then I see mistakes immediately and can fix them just as immediately. Not necessarily by removing the wrong letter, but by adjusting my thumb movements. E.g. if a "j" always ends up to be typed as a "h", I have to move my right thumb more to the right.
Works pretty well for me. But still, I hate typing on a smartphone!!!