I've only had my RC4 a few days now and I plan to keep it as my main EDC blade. I'm a skinny guy too btw.
I am using the kydex sheath horizontal with the blade tip end of the sheath just west of twelve o'clock. I have full range of motion while driving, walking, and bending. The handle just barely sticks out past my right hip but it's not noticable in a loose fitting shirt.
I would not carry this blade on the back of my belt like this because sitting would be uncomfortable. It's to big for vertical EDC in my opinion. The way I've been carrying it has been working great so far. Give it a try, just find the right belt so you can clip it right in the front.