<quote>Matt, in SF you can just has to be 3.5" single edge blade or less.</quote>
Smoke, I don't believe this is true. It must ben 3.5 inches or less to be legal even when carried unconcealed. No fixed blade of any length is legal in CA if it is concealed. I don't know if a pommel sticking out of a pocket would be considered concealed or unconcealed carry? A small sheath knife worn on the belt is considered unconcealed, and yes, it would be legal if under 3.5 inches, but you would get a lot of strange looks, and when you are trying to function in a white collar environment, you don't need those looks.
On the slip sheath subject... Tried them. Found you have to have the right combination of sheath shape, material, size, and pocket shape to make it work reliably.