What success rate should your HUGE rainbow tables have ?
I'd go for 99% (miss 1 in 100), project-rainbowcrack has opted for 96.8 % (miss 1 in 31.25), and that 96% looks bad in the eye of a potential buyer.
I think the Bruteforce point (bfpoint) should be between 1000 and 10000, but it depends on the desired chainLen.
3 rainbow tables for total success rates under 99.5%, 4 rainbow tables for >99.9%.
It's kind of blurry, this area, because if you have a fixed success rate and bfpoint, and you create a 3 rainbow table set, it's smaller in size than a 4 rainbow table set, < 5. On the other hand it takes more to generate. I can give you an example if you want to find out exactly the tradeoff between them. For large keyspaces i suggest we create sets of 5 tables in order to generate them faster. But if you have time and CUDA enabled devices I'd say we should go for the best configurations : less rainbow tables / set.