I had wild synodontis mutipuntatus and have breed these with my mbunas and peacocks, I would say I got like 50 fry in over a yr, I strip them out of the females, the baby cats were already feeding on the other fry. These cats do grow fast. I get like 1-3 fry each time I strip a female.
Breeding them with fronts do not work. Neither will tropheus. The size of the cats eggs are smaller than the mbuna eggs, and much smaller than frontosa eggs (front eggs are as large as popcorn kernals).
I also did breed synodotis petricolas, I believe I had batched of eggs in a container filled with marbles, 3 times, I placed them in another tank and lasted about 3-4 days, did see the wigglers, but somehow on the 4th day, it dissolved. These cats takes forever to grow, could take like 2 yrs to reach adult sizes. I gave up on these kind.
I have not heard any other success on other kind of synos.