You've ridden the 50 for over 100km and it feels good to you. Why not get it? With the 52, you're guessing it would be a better fit. That may be the right guess, or it may be the wrong guess. At least you won't be guessing with the 50. Personally, I wouldn't like a bike that touches my sack while standing over it. 2cm of clearance is perfect. BTW, you're not maxed out on the adjustments. You can always get a longer stem or different seat post to make the bike feel bigger. These aren't big investments and if it turns out not to feel better, you can just go back to the original parts.