This is my first blueprint, inspired by others minimum widht/max speed ships, this one has a top speed of 750 km/s. As it's a very long ship you'll need to apply the blueprint several times as the ship is built.
It's an endgame ship, it needs Aquilo technologies (fusion power and railguns), and almost all components are epic quality. I didn't test it with lower quality components, so I don't know if it'll be viable.
It doesn't have any speed control circuit limiter, but it'll probably be necessary if you try to fly through a dense asteroid field (Solar system edge and beyond).
For the fusion reactor to start needs manual input of Cold Flouroketone using a Assembling machine for emptying barrels. After that you can remove it. After that, it only needs fusion power cells to run.
Any feedback will be welcome.