[Spaceships] Powering smaller systems

[Polkageist]

I looked around the forums, but I couldn't find a definitive answer to some of these questions.

If you have a high-energy system in a smaller-system type situation such as a 1/3 sized weapon, contragrav lifter or mining system is it required that they have their own dedicated 1/3 sized power plant? Or can they draw power from the ship's full sized reactor, and how much power would they draw? Would it suck up a power point (as I'm inclined to assume) or would the smaller systems be small enough to make their power draw negligible to some degree? Perhaps just add up the number of smaller high-energy systems and round to the nearest whole number, that is 1 uses no power, 2 and 3 high energy small systems would use a full power point.

Also, I noticed that the Engine room never is mentioned in any special treatment for smaller systems. Does a smaller sized engine room prevent the HT loss from the ship or is having one an full-sized-or-nothing proposition (i.e. banned from being a smaller system)?

Please, I am eager to hear opinions and facts.