Thanks for the replies!
Yes, Astrophytums like the Seleni stock. I grafted lots of other Astros on this stock with pretty good results. I always try to select the thicker Seleni pieces, because of their higher resistance and growth speed. To get such thick pieces, you have to feed them well (using larger pots) and expose to direct sunlight.
Selenicereus is, like Pereskiopsis not a permanent stock and after 2-3 years you'll have to degraft or regraft to other stocks.
Best regards
Alex