Major Stress, so I'm guessing 22 Cobalts, 10 Javelis, 10 Gardas, 5 Perchiriens, 2 Kols, an Akkan and a Dunov should be about right. Or do you think I need to increase the number of flak frigates?
Ron Lugge, I like the Sova as well especially once it levels up enough to carry four squadrons. I've had the Hoshikos and a single Cielo before, but I must've been using the Hoshikos wrong.
Advalary, it's for an offensive fleet. I usually leave a single Sova plus six light carriers (2x fighter, 8x bomber squadrons) in more important planets. So far, they're usually enough to bolster the planetary defenses against pirates and the small raiding groups that the AI insists on sending.
Psyleck, I'll give Hard AI a try. As it is, my 440 supply fleet of 11 cap ships has been rolling over everything it encounters from the Medium AI.
My current fleet composition was the result of one of my mixed fleets getting eliminated when I tried to take over one of the AI's planets. That fleet consisted of the following:
26x Cobalt Light Frigates
14x Javelis LRM Frigates
8x Garda Flak Frigates
4x Perchirien Light Carriers
12x Hoshiko Robotics Cruisers
1x Cielo Command Cruiser
2x Kol Battleships (TDN Karamazov and TDN Proteus, levels 7 and 5 respectively)
Supply cost: 378
Credits: 26,475
Metal: 3,605
Crystal: 1,950
I realize now, that a big failure in this particular fleet composition was the over-abundance of Hoshiko Robotics Cruisers and the lack of supporting Battlecruisers such as the Akkan and Dunov, but I had thought that the AI knew what it was doing when it built 28 of those Hoshikos.

After this force got wiped out, I reloaded a saved game and scuttled most of my frigates save for the Javelis LRM frigates. My new fleet consisted of the following:
14x Javelis LRM Frigates
8x Kol Battleships (TDN Karamazov, TDN Proteus, TDN Krosus, TDN Logonis, TDN Kinesia, TDN Vigilus, TDN Krasev and TDN Achronus - Karamazov at level 7 and all her sister ships at level 5)
Supply cost: 376
Credits: 27,150
Metal: 3,550
Crystal: 2,350
I'd taken five planets while losing at most 1 Javelis, until I finally lost them all and decided to replace with the TDN Lazarus (Marza-class). The current fleet, augmented by TDN Aceron (Akkan-class) and TDN Numenia (Dunov-class), has taken over nine planets without a single loss and now carries 14 fighter squadrons and 7 bomber squadrons.
The only micro-management I do with my current fleet is to focus fire on the greatest threat and angle my fleet to points of least resistance. Previously I had to make sure that the Javelis were safe from getting killed --- not an easy proposition when the AI's bombers start going after them and you have to micro your fighters to intercept. The mixed fleet I had above was even worse, with the Flak frigates seeming to be ineffective.
I would really like to use a mixed fleet, but against the current AI (Medium), I don't see the point. I'm sure this will change when up against a human player, or possibly against the Hard AI. I'm curious though, how much micro-management is involved with your mixed fleets? How do you ensure that the Gardas actually do protect your fleet from the enemy's bombers and fighters without having to switch your attention from attacking the enemy with the rest of your ships?