Pretty sure Allen is a right D. He shoots left but was on the right side in pre-season. The d-men he paired with were Staal and Falk. Allen played well. Calm with the puck--low panic threshold--skated well--defended well. Seems to have a little bit of offense to his game as well.
It should be LD--McDonagh, Staal, MDZ, Moore, Falk, Johnson, Skjei
RD-Girardi, Stralman, McIlrath, Allen, Bickel, Syvret.
Take away Girardi and/or Stralman--the right side is going to be a lot weaker. Take MDZ or even Moore out of LD and we're still pretty good. We probably could even manage without Staal. Agree with your assessment on both McDonagh and Staal--the more ice time the better they play. So both DZ or Moore are there to swing a deal if you get something back that you want--though it's nice to have extra D around going into the playoffs. Between Moore and DZ I'd prefer to keep Moore--bigger, better skater. Think Moore's skating would make him a better fit for the right side on the 3rd pair than DZ.
Back to the right side for a moment. Best case scenario is that one of McIlrath, Allen are in the NHL by next year. Younger players--cheaper contracts more cap friendly enabling more $ to plethora of free agent signings next year. Rangers cannot afford to lose both Girardi and Stralman and I would prefer both return next year with either McIlrath or Allen taking the bottom pairing job.