I had a grafted Rebutia, it had 20 scions, I took them off and they all lived. Would this work for you, I really don't know, it worked for me. Norma

If you give the stock plant in increased amount of pot space to grow, when it needs it, the stock plant will continue to grow, IME. You'll just want to cut off any offsets of the stock plant so all of the growing energy goes into the stock and the scion.

I have made many temporary grafts on Selenicereus grandiflorus, but I have never tried to keep them for long (I have degrafted the scions). I know that they easily become top-heavy and start to lean, if the stock grows in diameter it does so too slowly. In your case it might be best to bury the stock. What kind of miniature cacti are they (how big do you expect them to become)?

If the scions are really difficult plants on their own roots then re-graft them later on a stronger stock like Echinopsis, Harrisia jusbertii or Stenocereus griseus, instead of just cutting them off and rooting them.

Jordi

Thanks for all of the nice suggestions from everyone. I guess I will first wait and see if I get more growth from the stock plants and if so my problem is solved. If not I will probably just have to re-graft.