Hi… the first publication  on tree pruning basics did help.  I am wondering, since I did not prune in  summer , if I could prune back those three headers  (of the sweet cherry grafts) that are so tall now, or if I should wait until winter.  Here is the section of the publication that was most helpful and notes this habit of sweet cherry trees!  I underlined a couple of sentences.

At planting, head nursery trees at the height you desire for scaffold branches. Train sweet cherry trees to the open center system (figure 5) with three to five scaffold branches. Young sweet cherry trees often grow vertical limbs 6 to 8 feet without branching. You must head them to induce lateral branch formation.

Prune in summer to reduce the re-growth of vigorous trees. If a young tree is growing very rapidly, cut off a foot or more of new growth after about 3 feet of growth has been made in the summer. This will cause branching. You can hasten production by tying down or weighting limbs to horizontal.

To promote branching on trees not pruned in summer, head every shoot in winter to about 2 feet.  

So my questions are… can I prune these three headers now, and can I prune them back to 2-3 feet above the ground, to be even with the Montmorency branching header.

Thanks…