Well, to answer the question, yes, a 10gal tank is okay as a holding tank for a female saulosi, and you should leave them alone in the tank they're in until the female is already holding, THEN move her.
On a side note...msobo and saulosi are not a good mix in one tank. Males of one species are very, very similar looking to males of the other, and females of both species are practically identical. The chances of hybridizing in this tank are extremely high, and personally I don't feel you could ever trust any of the fry they produce. On top of that, even if you keep the fry and grow them out, the species are so similar in appearance that you probably wouldn't even be able to tell they were hybrids as they matured.