OK, I finally found a rule that doesn't really break any classic Book 2 design while nerfing the size class A munchkin designs.
Take the book 2 Power Plant letter and multiply by 4. (Note that this is at best 2 tons of fuel per energy point and twice the book 5 usage.)
So the Type C cruiser requires 240 tons of fuel for the jump drive and then its Power Plant-M requires an additional 12 * 4 = 48 tons for a total of 288 tons and it still has extra fuel for its small craft.
-HJC
Take the book 2 Power Plant letter and multiply by 4. (Note that this is at best 2 tons of fuel per energy point and twice the book 5 usage.)
So the Type C cruiser requires 240 tons of fuel for the jump drive and then its Power Plant-M requires an additional 12 * 4 = 48 tons for a total of 288 tons and it still has extra fuel for its small craft.
-HJC