Hi Ibis,
I find the mix you use has a lot to do with your unique growing conditions. Being in FL where you can have hot/humid summers, I would give the cactus mix a try. You also get summer rains don't you? If so you would want your mix to drain very fast, as heat/humidity can quickly rot your semp. You can even place the container in a spot that is protected from rain, thus controlling the amount of water your semp is getting.
Hope this is helpful information for you?
