Crittergarden, I grow semps and sedums in trough-style hanging baskets.
There's obviously very good drainage because of the coco fiber liner, but I also use a well-draining soil mix. I mix my own, using tapla's 5-1-1 mix, which is 5 parts screened pine bark (no pieces bigger than 1/2 inch), 1 part coarse perlite, and 1 part peat moss. There's also a bit of lime to counteract the acidity of the mix and a slow-release fertilizer as needed.
I've never lost a sedum or a semp in these baskets, but none of my delosperma survived the winter, either in the ground or in the basket.
