It's already scaled in terms of cost and power output, so the extra weight makes no sense. Why have the D ultra light then? Because it gives people a reason to choose it over the C/B/A plants that they don't offer. It's also scaled based on income of the game. So if the B is extra heavy, there's got to be something to make it attractive over the C and A.
It's cheap. It gives you a benefit (more power) at a moderate cost. In game you have a choice whether to run a heavy powerplant which powers extra stuff or skimp on power and run a more maneuverable vessel. It's a good balance and allows flexibility in builds.
None as far as I can tell, only what I've been hearing on the forums since I got here. And you're right, some stuff floating is bunk - like the sensors improving gimbaling lock.
And for that falsehood, people demanded evidence, and none was forthcoming. But for months and months this misinformation was spread because people had heard it on the forums. Can you see where I'm going here?
However, I think there's every reason to think this is the case for the reasons stated. If the extra weight has no offsetting advantage, then its existence is pointless. Feel free to test it out on a Sidewinder or something, have someone knock your PP with pulse laser and count the hits.
Aha, the old switch-the-burden-of-proof-to-the-questioning-party-defense. You are the person who is claiming something that is not supported or advertised anywhere (apart from 'people on the forums' which is hardly a good source of accurate information) is true. It is up to you to prove it or stop spreading misinformation.
I detailed in one of my previous posts how to get an indication of whether it's true, compare the integrity between the plants. If it's higher in B than A and C then mass is directly related to integrity, which has been stated by developers as a measure of how hard it is to take out.
I would have already done it if I was not located 7kLy from Sol, a 7 hour flight to the nearest station )-: