Pereskiopsis Spathulata is a great cactus for grafting seedlings onto. Despite the fact that it doesn't really look like a cactus owning to its leaves these cacti are incredible fast growing and readily root from cuttings. They are also drought resistant while being able to handle frequent watering without rooting.

 I've never been a great fan of grafted plants but but started grafting in an attempt to save albino seedlings and other rare lophophora. This proto- cactus does not look like other species but is extremely fast growing and is particularly suitable for the grafting of tiny seedlings. Be warned however that the grafted scion may quickly outgrow its stock plant and may need re- grafting onto more durable stock or re-rooted once sufficiently established.

The image below is of a grafted seedling that is four months old. The scion (lophophora plant grafted on top) is only four months old but about the same in size as a plant that is three years on and grown on its own roots.