The Hull Speed patch allows one to adjust the overall speed of a ship based on the size of the hull. By editing the TechTables.txt spreadsheet, you can add a 'MaxSpeed *= X' tag to the 'Tag_Values' of ship hulls (where the X value is the multiplier you wish to use). The multiplier will then be applied to the overall speed of the ship.
This can be useful in one of two ways. First, you can make smaller ships very fast, allowing them to close quickly with the enemy and attack. Second, you can decrease the amount of space taken up by engines on smaller ships, but have them still able to travel as fast as larger ships. This lets the pack more weapons on board.