There are some shorter asian and hybrid varieties of winter hazel that might work in that situation.

How about Juniperus procumbens 'Nana' on a high graft? I'd also add at least a third element as well since it's 30 feet long.
tj

Here is a link that might be useful: Hang 'em High

Keep in mind that the Aronias will sucker and thicken up in a few years. But 3 Aronias in a 30 foot section is not much. You have room for a great many other shrubs. I'd group all three togther, then add other shrubs. You don't want the area to look polka dotted especially since it appears you're trying to keep the planting very narrow with only one layer to it.

Thanks for the great suggestions. I have rethought the hedge idea, and I think instead I am going to create some beds using some nearby trees to use two of the chokecherries, and I placed one towards the back of a mixed shrub/perennial bed that had a bit if a gap in it. Can't wait to see these grow!