What I'm really curious about is the lower limit of Qi Sea, or rather, 2-star Body Refining. Like, if the PH limit was 50 and the EX start is 120, I can't even give a good estimate of what it will be for Body Refining, since the limit for 1 star is already 100 (or more). Call me deluded, but I bet the start of 2 stars will already be stronger than an Middle Xiantian.
Not to mention 3 stars, which TW himself stated that when the MC reached it, no one on this planet would be a match for him... And this was when he was well aware of how powerful Yichen is.