I don't have anything in its weight class, so I took a 3M heavy rails/missiles ship and two 1M brawlers. They took it out after taking about 900k in damage. I did micro my ships, especially the one with rails, and against another human I probably would have lost.
Your ship is a lot faster than I would have guessed, which is good. Like someone else said rails are going to be an issue for you. I had a pair of 525% rails that went through your cannon decks pretty well, one rail would punch through and do damage while both at once would destroy whatever they hit. You do have enough cannon that any one ship is going to get hurt pretty bad before they do enough damage that your fire rate is ruined, and anyone that gets to that point will probably have taken quite a bit of damage from missiles. My own missiles didn't do anything until half your ship was mangled, but that's not really surprising given your PD.
I was able to shoot a couple missile compartments loose though, consider adding some connecting structure in more than just the corners.
Your doubleshielded areas held up a lot better, though the side-facing shields don't really do anything. You could cut those out, and put some armor over the middle of the compartment, leaving just two walkways for feeding the PDs out there. You could also put some EBs in there, your ship is fast enough to hold someone in their range and that plus cannons will wreck most any defense. Putting in some weapons would also tempt people to attack your most heavily shielded parts, which can only help you.
The back of the ship seems pretty pointless, and given what you already have elsewhere I don't really know what to suggest there. You could copy your front onto that whole side, which would help with flankers and allow you to swap broadsides when a single ship manages to damage your front, but it also adds weight and cost, and doesn't help a ton against a single enemy ship. ... Actually, you could copy your front onto your right and your missiles onto your rear, and fly diagonally. It would be easy for you to rock from broadside to broadside, almost doubling your firepower and tankyness, and all your missiles would still be able to fire since they have a 270 degree firing arc. Your ship would also be even faster than it already is. IMO that's the single best thing you can do at this point.
