It will fall over and grow all over itself but that won't hurt it. Trying to keep it trimmed to 7' will be futile. Let it fall.

You should hard prune all of them next year in early spring to encourage fullness at the bottom.

Agree with BorS. In nature, cascading down over themselves is what clematis do when they run out of things to grab onto.

I did cut them back to about 10 inches above the ground this spring. Should they go lower than that?

KPW, I normally cut my type IIIs back to about 3 to 5 inches from the soil. All you really need to do is leave a couple of leaf nodes above ground. In one book, and I think it was in John Howells book, "The Troublefree Viticellas, he suggests cutting the viticella and related cultivar,of which Jackmanii is one, all the way back down to ground level. I haven't gone that extreme yet.

You don't need to cut them again this year. That will be fine.

Is there room for the 2 outmost jacks to be trained sidewise across the top of the fence? Or a tree or telephone pole nearby that you could attach a rope to and tie onto a trellis?

Maybe next Spring you could prune some of the stems even closer to the ground.

Marie in ME

Should I also cut the Henri's back as hard? They are in group 2 for pruning. I've read varying points of view on group 2 pruning.

KWP, all clematis the first year or so in the ground should be cut back regardless of pruning group to encourage root development over top growth and to produce more vines from the crown. If the clematis has been in the ground for several years, whether to prune it back in the early spring depends on how vigorous the plant is and how many stems you have coming out of the ground. If it flowers well and has multiple stems, then leave it alone. If is scraggly with few stems and few flowers, cutting back just rejuvenates it.

Agreed! Since they were just planted last summer. Cut the Henryi's back hard too.