Hmmm......
I would start by adding wedges, which helps a lot. You may also want to make it longer, it looks a bit stumpy right now. Try making covering up your thrusters with hull, then putting a hollow tube 2 blocks long on the back, and putting ice crystals or lava in it, to make it look like engine glow. some wings would help to. I would get rid of the cannons, as there is no way that thing is ever going to stand up to an isanth, so you may as well run unarmed. Putting salvage modules in an array with multiple outputs is better than a single more powerful beam. I would suggest playing around in creative to learn some shipbuilding.
You also want a better power setup. Put the power modules in long lines.