Answer: With clematis, there is a rule of thumb that says first year they sleep, second year they creep, third year they leap! In other words, this is a plant that takes several years to become rooted and fully established before it grows to its full potential. It sounds like yours is behaving normally; sun all morning to early afternoon is fine.
Most vines are big plants, with the exception of some of the clematis that fall into the smaller and midsize range for vines. You might try a clematis along with your climbing rose, or you could consider an espalier (pruned and trained to grow flat against the wall). Depending on the width/depth of the space you might be able to train an apple or crabapple tree there, for example. Another option might be one of the taller Explorer roses (such as William Baffin for example) which would top out around 8 feet or so and is fairly manageable against a wall, although as with any rose you would need to thin it, tie it, and train it onto the trellis.
Your local professionally trained nurseryman might have some other suggestions based on a more detailed understanding of the growing conditions where you want to plant and your overall design goals.
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