[Arran]

Ron;
  The method that Bob Andersen uses is to uncrimp the bottom of the electrolytic can, which I tried on a junk can I had laying around with limited success, then to extract the old innards with a cork screw and a heat gun. Then you replace the old caps with new radial lead jobs and run the leads through small holes drilled in the base, replace the can, recrimp the can. He has had great success with this method, I have not, and it could be a pain should the replacements themselves need replacement in the future. A variation on this is to file the crimp off the bottom so the can can be removed and replaced on the base, but then both the ground ring and the can have to be glued onto the insulated base.
  The method Mike "Morzh" uses seems to work well, he cuts the can maybe 1/4-1/2'' higher above the base, this leaves a flange so you can fit the rest of the can over top, I think he uses a pipe cutter for this, the rest of his procedure is the same as the two above as far as I can tell. One method that I have used is to use a pipe cutter to cut the can further up, and to resecure the top with aluminium duct tape, actually I haven't use this on a twist lock can yet, it was on an axial lead type with a cardboard sleeve.
 One I have used on electrolytic cans, ones with a threaded base in a mid 30's Rogers set, was to couple the two ends together internally with a plastic pipe fitting, though you could use anything that fits the internal diameter of the cans, and then used hot glue to glue the can sections to the pipe fittings. I did not cut these cans, someone else did very crudely with a hacksaw at a random height, and not even in a straight line, so I had to wrap tap around the top and bottom sections and file them down to the edge of the tape so they would line up square. I lost about 1/4'' to 3/8'' out of the height of each can, they also used epoxy or some sort of rubber cement to glue the cans together, one of which broke apart whilst servicing the chassis, so I really had no choice with how to repair these.
Regards
Arran