Crossbreed is my choice for IWB, but carrying at six o'clock is a bad idea. If you should go down hard on your back there is a very real possibility of a spinal injury. Why don't you they carrying at four o'clock?
small of back is a bad idea. If you're pushed backward and fall onto your back, the gun becomes difficult if even possible to access, and you can incur severe spinal damage falling on it.. especially if you slip on some stairs. That said, if you insist on it, look at Link Removed
He doesn't have it listed on his page anymore, but he does make a really nice leather IWB SoB holster. Just contact him and ask.
If you want the best access to the gun, consider appendix carry.
It's also probably the slowest draw you can get, certainly the slowest from a belt position, and makes it pretty much impossible to defend the gun, and makes it difficult to access the weapon when seated, besides the falling hazard that others have noted. I have heard it called the 'widowmaker' position.
If you want to use the small of the back carry your shoulder arm and flexability is very important. The gun can be canted , but it will ride deeper making it hard to draw. It is more than any position to carry a game of trade offs. A gun with a bigger handle like a 1911 is easer to grab, but prints a huge amount if you Bend over.
I would suggest a compromise. Behind your hipbone. It's much easier to get a hold of, does not print when bending as much and still gives most of the advantages of small of the back carry