Hard to say. All you can really do is give it a try in your garden and see. HMF looks like it lists it in a couple of zone 5 gardens. Maybe you could contact those growers and see how it does for them.

its possible. It seems my only chance is to get it close to a wall and mulch it to all hell. To be fair I have never tried mounding soil.

Evening Star should do well with mulch in zone 5. I grew it by the sea where gale force winds in the winter hit it and it never even had any dieback. IMO it is one of the best white floribundas. No disease and good vigour. Don't think it had any fragrance.