DCP-o-matic

Hey folks,
I need to make a DCP for a feature that is 2.17:1 and play it on a screen that is a fixed width flat screen with horizontal masking that is adjustable at the top of the screen. I think my best bet is to put it in a flat container and bring the masking down to fit as opposed to putting it in a scope container where it wouldn't fill the screen side to side. Is there an easy way to create a flat DCP with the image set at the bottom of the container or is my only option to have it centered in the container and then set my projector presets accordingly?

If the masking can only come down from the top - isn't there a projector preset able to deal with that (vertical shift down)?

I once did a DCP with top-only padding in order to place subtitles there. However, I used a letterboxed scope source file for it, so I only cropped away the bottom letterboxing and kept the upper one in DCP-o-matic.

Yes, I can definitely create a 2.17:1 screen setting on the projector. I was just curious if screen positioning within the container was a DOM option that I hadn't discovered yet.

I don't think so. Only if there is some letterboxing in the source file.
I also opted successfully to include an 'unscaled' option that would allow to center lower res footage on screen. But, only center, no special layouts.