tbh there is too many variables to give a definite answer as to how many you should field.
ideally you pair 1 of them with a capital ship as escort, perhaps along side with a LCV. for low priority games, you field them as the main battle line and if you need support for your capitals, use the LCV.
For larger FAP games you could either field them like escorts and or groups that guard your center. They have a good defense system (2I/2AF and Hul 6), making them tough enough for you to abuse by letting them follow a spearhead.
They do pair up nicely with a Posidon, Apollo Bombardment, Hyperion and a Marathon, as long as the later doesn't out pace them too much. The rails on the chornos would help during broadside exhanges with these capital ships with the opponents.
Omega's and Warlocks can be rely to hold their own without escort support. Then again this depends on how you field them.
The Chronos does contribute to defeating interceptors and stealth, finishing off cripples, act as a initive sink along side LCV and Hermes, and can brawl with other skirmishers that need to close distance on your capital, and assist at knife range. They can punch through screening units but they're not ideal for roling as hunter-killers, especially when compare to Narn and Centauri selection for example.
hope that helps you
