Yes, looks good so far. What soil I can see in the rest of the bed does look kind of heavy. But if you mixed the cactus soil and the sand and whatever rock you found into the soil right where the semps are planted into, they should be good to go. Looks like you took Lynn's suggestion of tucking some rock/grit under the heads which should help with keeping the leaves from rotting. If you are worried about whether the health of the semps in this location, you can always reassure yourself with a few offsets from here planted elsewhere in case this location doesn't work for some of them. Your strip of bed looks ideal for dropping a shade cloth right over bed on really sunny days (...are there sunny days in Portland?)
In my experience, the few arachnoids I have didn't do well in my afternoon sun semp bed. I had to pull them out and put them in a less sunny spot.
