Investigate Pacific Wax Myrtle. Grows bigger than 7' x 3' but develops rapidly, could be pruned to control size. You will wait a long time for a Japanese Holly to grow 7' tall under ordinary conditions.

Pacific Wax Myrtle seem to be a little uncommon around here still and command a fairly high price, but I found one at one of the specialty nurseries for $30 earlier. I've been having some issues with my soil and nothing has been putting out any new growth, but I have new leaves coming up on my PWM, and I really like the smaller foliage!

Since it can get to be a LARGE shrub (and rather rapidly), PWM are not so common at urban nurseries as they are in more rural settings. And there is a big demand on them for agencies and commercial installations that require native plantings, so often that exceeds the supply.

I am in Kitsap county also and PWM are used frequently for informal hedges/natural screening in this area. I just spec'd an informal hedge of them for a design client in Poulsbo and we had no trouble locating the size and quantity we needed. I do believe attempting to maintain them at a 3' width is counterproductive to the natural habit of this plant - it will want to get much wider and puts on growth rapidly. I've yet to see many of these formally hedged - typically they are left to develop a more natural screen.

I'd investigate something like Euonymus 'Green Spire'. This has a very columnar habit that will keep the width to a much more manageable size than PWM without frequent pruning and grows moderately rapidly to 6-8'. Not an uncommon plant or hard to find either, and in decent sizes. One of the smaller leaved, more compact ceanothus like 'Dark Star' could work also. These take shearing/hedging very well and will develop the appropriate height relatively quickly.

Pacific Wax Myrtle standard item at local independent retail outlets here for years. I was just noticing how dense some 5 gallon plants were at a nearby place this week.

Parking lot planting at Lynnwood CostCo has sported ridiculous tightly sheared examples of this plant for some time. I have also seen sheared examples elsewhere. Clearly able to tolerate close clipping. Good response to tip damage not a surprise for a shrub native to outer coastal habitats, where it is subject to high winds laden with salt.

Thank you for the suggestions. I'm in Poulsbo also. The more I look at my space, I really think I may need to go with option 2--the trellis!