C. armandii is a BIG clematis! Will easily grow to 15-20' plus. One at my current garden grew up into a 40' tall horsechestnut before we had it removed. At most, you could use 3, maybe 4 of them. If you cram in more, it will just crowd the plants and they will not thrive.

Thank you gardengal! We’re in PNW zone 8b as well. This is very helpful. I think we’ll go with one per panel, so 4 total. I didn’t even think about overcrowding.

Our neighbor actually has two of them planted, you can see in the rear of the photo, about 6ft apart. Not sure how long they’ve been growing, but they’re well established and thriving.

One C armandii could potentially cover the whole fence. Two if you're in a hurry. 15 metres height is not uncommon.

I agree 2 to 4