It's as stickman says. Personally, I just really really like the middle key, it doesn't necessarily feel wrong for me to use my thumb to hit the spacebar. I find the ring fingers mess me up more as my perception of 2nd and 6th lane vs 1st and 7th gets messed up at certain times. Other than that, pretty fun... but I like 4K more. I have tried some 5K, it is definitely my cup of tea also.