*Okay* is the classic camcleat with roller thingy. See the
application notes for the camcleat CL253. There are rings with pulley, or you can attach a pulley to a ring for the bottom. The problem with such a system is where to attach the shockcord. Most people attach it to the ring which has the unfortunate side effect of pulling it down away from the hook. Bad.
*best* is to put the camcleat on top of a double pulley like the Marstrom
carbon block.
I can't find a good pic, but I'm sure someone has one somewhere. You fix the camcleat to the wire/line in the eye under the handle and make a 2:1 to the double pulley. On the second pulley you pass a line attached on one side to your trapeze ring (or ball if you want to go to the best and use a Bethwaite system) and on the other to the shockcord keeping it in place, with a ball to stop the line. See the "no-cut hi-low trapeze hardware kit" page 48 of the Murray's catalog for inspiration, noting that the clamcleat is missing the crucial D plastic ring listed in the clamcleat application notes. Think about it, and you'll see why you need it.
Typically on a two man boat only the front trapeze needs to be adjustable as the range of position the crew can move to is varied. The skipper usually doesn't move that much and doesn't need the added hardware/expense.