You should be aware that the wooly adelgid is killing hemlocks all up and down the east coast.

Privet isn't totally evergreen, and is also invasive. If you want a hemlock, I would recommend one resistant to the adelgid. Any variety of Canadian Hemlock would be a poor choice. There are others, that are less commercially available, unless you know where to look. Tsuga diversifolia, T. chinensis, and Tsuga sieboldiana (sp?) would be better choices. In my area of the US, they are experimenting with T. chinensis as a primary understory replacement for T. canadensis. Beware that much of what is sold from nurseries is T. canadensis, which the adelgid is polishing off. I'm not sure what you mean by Jumbo Hemlock?

I have also seen other evergreens such as Eastern White Pine (Pinus strobus), Norway Spruce (Picea abies), and Western arborvitae/Western Red Cedar (Thuja plicata) used as understory trees with success.