I retrofitted a 500 ton asteroid with ion thrusters. Now I have a spinning asteroid! You absolutely can not steer that thing. Center of gravity is way the forget off what I consider center. This game needs balancing thrusters to negate the CoG effect to some degree.
I also built a 6DoF ship. I call it The Explorer and I loving love it. Very light (58 tons), goes up to 15 ups in a few seconds, has all the crafting needs + lots of storage. The 3x3 energy core consists of 3 different types of reactors. There's 300 power left over too. The only downside is that it's very weak structurally but the steering is increadibly agile. You do need to be a little careful as turning/tilting in one direction too long will send you spinning. The thrusters are a tad bit too powerful. 48 thrusters in total.
Balanced symmetrical design. (The glass and crafting blocks weight barely anything so they do not affect steering.)
Targeting reticle for steering. It helps so much that you won't believe it until you try. Up direction has no glass so you can instantly orient yourself too.
Crafting, controls, and storage. I only have 3 chests on board because I'm a dirty cheater so I don't need any more space.
Oh look. It's 11PM. Where did the last +6 hours go.