Sky,

Stick with mono unless you plan on dredging 200' or better. Two things- first, there is absolutely no stretch so plan on losing a lot of fish. Losing fish will usually occur as soon as the fish comes off the clip or surfaces behind the boat. Another opportunity for fish is when he starts runing towards the boat.
Mono will keep the play in the line...

Second, 20# is pretty small for a diameter. 65# (PP) will put you fairly close to 20# (mono) diameter. As far as releases, an Offshore or Cannon adjustable should work ok with PP. If you are still experiences problems with the clip, make a large loop (3-4 inches) with about three or four twists then place it in the clip.

Save that stuff for jigging or mooching or off your DRs for the deep water.