Step 1: Freestyling the Lens
I will be using an old Dejur enlarger lens because that is what I have laying around here. Your lens will probably vary. M39 mount and old Argus c3 lenses work exceptionally well but up your cost considerably. When you have the lens the first order of business is to remove the lens on your SLR and hold your tilt shift lens up to the camera. move the lens back and forth to get a round-about distance to cut your inner tube. Mine needs about 3 inches from the mount to the lens. It doesn't need to be very exacting as the lens and tube will move in and out to make adjustments as you shoot.
Step 2: Attatching the Inner Tube
Step 3: Connecting Inner Tube to Lens and Mount
Now slip one end of the tube over the back end of the lens, just far enough up to have a secure hold on the lens. Attach a zip tie around the tube and lens and pull tight. Now place the other end over the mount adapter. This is difficult and you may want to work the rubber a bit to loosen it or failing that use pliers to stretch the material over the mount taking care that the tube and lens end up dead center in the middle of the adapter. Finally, zip tie the tube to the adapter and trim any excess ties and innertube from under the adapter to ensure a flush mount to your camera.