I ride ronix cells. I've played around with em a bit and have found that if i go too tight, my calf muscle gets really weak fast. im guessing from restricted blood flow. mainly on my rear riding foot. This resulted in wanting to take a shorter run, or not going for the jumps as big due to fatigue.
I found that if i flex my ankle forward (like if your landing or cutting toe side) while snugging them up as much as my hands would let me, i got the best fit. no numbness, while no threat of pulling out.
(havent come out yet, although i've ripped the screws out of the inserts. not sure whats worse.)