[Suicide Junkie]

OK, imagine that the standard QNP system has engines that produce 15 thrust points for every 10kt engine. Escorts could have an EPM of about 15 (so one ion engine gives them a speed of 1)
The frigate would have EPM of 20, and so on.

Jump up to a cruiser sized hull: 50 EPM, and the maximum speed before an RCE is only 5.
Because of that, we want to put a step before the Cruiser.

So, for these types of "Medium ships", we will reduce the scale. Division by 5 will work nicely in this case.
So instead of 50EPM, the cruiser now has 10EPM.
Instead of 15 thrust, the "medium ship-mount" engines only have 3 thrust.

Our cruisers can now hit a top speed of 25 without causing an RCE. (255 / 10 EPM = 25)
They also appear no different on the surface:
The old engines were 10kt, and it took 10 engines to move at speed 3. The new engines are still 10kt, and 10 engines will move you at speed 3. The only difference is that you have a higher max speed without an RCE!