I've never done the clumps because I think uniform spacing is better. If you look long enough on DWN website I think you'll see trees planted in uniformly spaced hedgerow type plantings. Rather than going 3 trees every 6-12ft just space the trees out 2-4ft apart. That's what I did this year in planting about 250 trees.

At a close uniform spacing you still get the advantages of clumps but the trees are easier to manage.

I don't know of a single experienced poster here who uses or promotes the clumps. Clumps are useful in a situation where landscaping considerations trump ease of management.

I had considered the hedgerow method as well. If that's recommended I'll go that route. What spacing did you use? Will it make a difference if my row is north-south? Given the space I have I think I could do 30" center to center. Is that too close?
Thanks!

On average 30" is about what I did with rows 6-7ft apart. If you've only got one row that's even better. They'll get plenty of light if you summer prune early and often. I've already done some tipping of branches headed the wrong way. And expect to do quite a bit of summer pruning starting next year.

NS is the best row direction. That way each side gets full sun half the day. And in NM and west TX sunlight is abundant.

I plan to control growth partly by irrigation and fertility. Not too much of either.