I have the Witness with wonder finish, in 40, 4.5" barrel. It fits in the Don Hume H715 model 37 -an IWB leather holster, which is for the Ruger P85/P89. The slide ends up even with the end of the holster, and the barrel peaks out a hair (remember, the barrel extends a hair past the end of the slide).
Now, if you holster the Witness in the 37, hold it over your foot, and turn it upside down, I can almost guarantee you a broken toe. Perhaps try that with the 3.5" model first

HOWEVER, once inside the waist band, the gun rides snugly. If someone has me upside down, by the ankles, I've got bigger problems then my gun falling out. In fact, if it falls on the bad guy's foot, that might buy me some time

I had a Witness Match, without the rail, and now wonder if it, too, would have fit. Sinced my Witness is a tad loose, that Match might be worth a try.