Congrats on making it that far 2d Gamer!
Only once in my entire life have I actually made it to the Cobra fleets in the sector where Solaris is and actually defeated one of them I think.(I can get to Solaris pretty easy on the trainer version with infinite lives) Sadly the second one defeated me... Talk about pissed... The Raiders and Mechanoids get downright nasty at that point in the game but are defeatable with practice,(take the Raiders and Mechs at long range if you can) the Cobra fleets however, are a utter nightmare. My only suggestions to you are to learn to track, target and destroy them as quickly as possible, which I'm sure is easier said than done. The added hazard of a red-zone will only seriously complicate things I'm sure... Now to the Cobra ships... Those things are a tough nut to crack as they are VERY erratic with movement and firing. However, I've had an easier time once I figured out a simple tactic, flying up and down to "scroll them up" then to the left or right without colliding with them near you for a quick shot. It's rather risky and not recommended if you haven't practiced it enough, but with practice you can get a much easier shot at them up close for a second, which is all you'll need if you're a good shot.
OH yes, not sure if you know this or not, but if your targeting computer get damaged, learn to use the numbers on each side for up-down and left-right position to try to pin-point your target. Didn't know what those were exactly for the longest time, talk about a eureka moment!
Bottom line, this game gets mind-numbingly hard when you see Solaris for the first time in it's sector 2d Gamer. By the time you get to the sector right before returning to the "Solaris sector" to take on the three Cobra fleets there and reach planet Solaris, is by far the most trying part, namely due to the red-zone. The Cobras however are VERY frustrating, even without being a red-zone. Shot placement and timing is highly crucial to taking them down quickly and without losing ships.
Here's a map of all the sectors by the way:
http://skintigh.tripod.com/atari/solaris.html
Hope this helps!