What is the soil like? The distance between them? Exposure and slope? Water source? I'd fully consider Ramblers recommendation as Sitka Pruce does grow well - under good conditions. Twenty years ago we planted those same super trees and I worry some. I'm on task though by inspecting the trees every season. Lost a few to the drought and the recent heat didn't help any but no sign of any abnormality. My site is in the Cascade foothills at about 1000'.