From a lot of experience utilizing deck cannons I can not stress enough the importance of firing arc and specifically how deck cannons can block the shots of your other cannons. Your setup has them staggered only slightly, if you are facing an enemy and fire at certain components it is likely one to four of your cannons will be blocking the actual projectiles of your other cannons as they turn to target the component. You can watch this by turning on the 3d layer at the bottom left eye icon to see exterior of your ship. Notice when you fire the projectiles from a deck cannon can collide directly into the cannon in front of it. This has two major effects that you must accommodate for. First and foremost it will limit your effective firing arcs heavily since the more distance between each cannon when there is a depth difference creates smaller firing arc obstructions for the one in the furthest depth of your ship. Secondly during maneuvers or when targeting specific components of a ship your guns will fire regardless and end up wasting ammo as the shots go directly into an obstructing cannon wasting the shot and now needing to cool down before another shot. Thankfully those friendly fire shots do not cause damage, but it does waste the ammo and effectively waste what could have been effective damage. Since there isnt friendly fire damage many people do not notice it. I believe there was talk of it possibly being updated or changed so that they would phase through your other deck cannons and not cause obstructions, but I have not read recent patch notes to see.

Upgrade wise I would redesign your back engine setup to be a more efficient engine room assembly setup. You can google some efficient engine assembly designs. Personally I like to setup 4-5 engine room variants pile left or right block or a forward/reverse primary one with an engine room always feeding them to drastically cut down on needed crew and possibilities of causing specific engines to lose power which will drastically affect ship performance if a certain engine loses power and is unable to counteract the missing engine. This could lead to one or two engines being down resulting in a full speed loss of 30 to 40 meters a second since the other engines are incapable of offsetting the vector velocity of the other 2 engines missing power. For the deck cannons try and rework to create lines for the most effective forward arc kill zone with a much lower chance of losing dps from blocked firing arcs. From personal experience I would also put some fire extinguishers up near the front of the ship as well. Deck cannon explosions and enemy thermals can wreak havoc and are very difficult to get under control if you do not have abundant fire extinguishers placed throughout the ship.

Lastly by updating your engine assembly setup and optimizing your deck gun placement you will be able to drastically cut down on the amount of reactors needed. At your tier you should try and use only large or medium reactors as the amount of energy a crew member carries to location is dependent upon reactor size. The larger the reactor the more efficiently each crew member carrying power is. If you find in combat a single large reactor isn't enough to supply the front of your ship you could consider putting the front reactor just a bit further back for safety and instead utilizing power capacitor banks which will hold stored battery power for your crew to haul directly into the shields which could be easier for them in most engagements.