I love your pictures. I have wanted to do this for a long time and have tried with small sedums. They grow too fast. I have tried semps, but have had no luck. We have very hot humid weather here in North Texas and I feel that semps don't like it one bit. I have thought I may try it with small mammalarias. Thanks for all your input and pictures.

You're welcome, Rabid and Welcome to ATP!
Can I ask if the Sedum you tried on the frames were successful in growth even if it was too fast in your environment? The reason I ask is that not all sedum grow at the same rate and not all sedum grow big. There are some that grow slow and grow small or clustered or viney. You just got to find the right ones that will work for your size frame. Especially if they will survive in your humid hot conditions...don't give up on them; you may just need to experiment.
Here's example of a small clustering sedum (Sedum brevifolium album) that I mixed in with my semp frame. Sedu growth has been there for 2 years.



Of course, not knowing your growing environment, maybe sampling some other sedums and seeing how they grow for you might be worth it to find out which might work for you. I find that growth that is too fast or too gangly can be controlled by regular pruning. This helps to encourage bushier growth.

Here are some sedums that for me have stayed small, grow slow and/or compact.