Hi there. I haven't grown anything along a stone wall but I thought I'd make a suggestion on clematis for you since you mentioned SAC but were hesitant!

There is a new clematis called Sweet Summer Love Clematis that I purchased a few weeks ago from a local nursery. It's similar to SAC but it blooms earlier, longer, and is less invasive than SAC. It has bright purple blooms as well. Since it's new I don't have much feedback on it yet but it looks very promising. Good luck! I'm sure you'll find something just lovely.

Michaela

Here is a link that might be useful: Sweet Summer Love Info

I visited a garden this summer on a Garden Conservancy Open Days tour that had clematis and climbing roses growing up a mortared stone wall and along the top which was probably about the same width as yours. They had used screw eyes and thin wire to guide the roses and clems up the wall and along the top. Lee Valley makes a trellis system that uses wire and some type of epoxy to attach the fasteners, and I've attached a link below to one thread, but a search on this forum (scroll down on main page to just above the new post section) may turn up more thread on it. I don't have one so I can't give an opinion.

Here is a link that might be useful: Lee Valley wall trellis