moving this down

I cannot answer your question specifically, as I do not grow any of the clematis you have mentioned. Perhaps someone with experience with those varieties will add their opinion for how they would perform in your hot climate.

I do have another suggestion though. Silver Star Vinery has a new viticella hybrid named John Howells, after the man who wrote one of my favorite clematis books: "Trouble-Free Clematis: the Viticellas". Viticella hybrids are known for being more heat tolerant. I added John Howells to my garden this past November, and it has just opened its first flowers this week. They have a velvetly texture and a white reverse, although the flowers would be smaller than the others you were considering.

I've included a link to Silver Star Vinery's "J" page - you need to scroll down the page to see the photo. I think their photo looks pinker than the flowers on my plant - I don't know if this is from different growing conditions or just a problem of the camera accurately capturing the color. I am not aware that anyone else is currently carrying this clematis yet. It was raised by Wim Snoeijer who also raised Inspiration, Little Bas and Mienie Belle - all of which do really well for me.

Here is a link that might be useful: John Howells at Silver Star Vinery

I have Rebecca, in its second year, but none of the others you mentioned.

My Rebecca is growing on an arbor next to Candida; both were planted at the same time. Candida is double the size of Rebecca and has much thicker, straight stems. Rebecca seems to twine around itself and so is lower. The color of her blossoms is beautiful but not the bright orange red shown on the Klehm's Song Sparrow site. For me, they are a deeper red and smaller than the 6 inches advertised on Klehm's. I bought her at a local nursery, not online, and so I was aware of the difference in her coloring compared to how it was advertised on different websites.

I think that "red", in Clematis, often contains blue, purple, or black, so it's kind of the "holy grail" of color. Hopefully others have experience to share and can help you in making a choice.

Molie