You're looking through the
wrong end of the telescope.
If a power plant is Rating=1 in X tons, it produces 1xTons/100 EP and always does -- as you see it (and, again, I mostly agree!) However, if the performance table says it produces a different value (due to rounding effects) in a different hull, that's what it produces in that hull according to the rules as written. So, per RAW, drives T, U, and V in a 600Td hull produce exactly the same quantity of EPs despite being different sizes.
EPs are already rated by hull size.
As advertised ... people are looking at this through the
wrong end of the telescope.
I was hoping I wouldn't need to explain what that meant (in this context), but it appears I have no choice.
Let's look at this objectively, shall we?
There are two methods for dealing with this issue.
- USP controls what can be put into a craft.
- USP simplistically describes what has been put into a craft in a concise and convenient format.
The purpose of the
USP is mainly to simplify LBB5.80 combat resolution.
I contend that the
USP values are a RESULT of what gets built into a craft, rather than a determinant of what CAN be put into a craft when designing such a craft.
For example ...
Let's say we're working with a 700 ton hull (to disambiguate the implications of what I'll be outlining) @ TL=11.
We want max acceleration and agility, so achieving Agility=6 in a 700 ton form factor will cost 42 EP.
The highest computer model available is a model/5 (3 EP) and we want to arm our craft for a system defense role, so 7 hardpoints with turrets on them.
We want 1x triple laser turret (3 EP) for "shots across the bow" type stuff. The other 6 hardpoints will mount triple missiles and triple sandcasters (0 EP). The craft will have no screens (0 EP).
So the total EP demand for this craft is: 42+3+3 =
48 EP
Question:
- Is it possible to build a power plant in a 700 ton hull that generates 48 EP exactly (no more, no less)?
If you're "working the system" the way that @Grav_Moped and @mike wightman appear to be doing, letting the USP "control" what is available to choose from, the answer is a resounding NO. 
You can have a power plant that generates 42 EP (code: 6 @ 700 tons) or 49 EP (code: 7 @ 700 tons) but you CANNOT HAVE a power plant that generates (only) 48 EP (code: 6.85714286 @ 700 tons) because you can't put a floating point number into the USP, only integers.
This in turn means that @ TL=11, your power plant must be either 42*3=126 tons (code: 6, 42 EP) or 49*3=147 tons (code: 7, 49 EP) ... but CANNOT POSSIBLY BE exactly 48*3=144 tons (code: 6.85714286 @ 700 tons). ANY power plant tonnage that is not a "multiple of 7" is simply NOT ALLOWED. 
Do not pass GO.
Do not collect MCr200.
That's "one way of looking through the telescope" of possibilities for how to build craft using LBB5.80. 
The other way of doing things (which is basically "looking the OTHER way through the telescope") is to start with the EPs you need, determine how many tons of power plant you need to supply that and then "simplify" the result into something that can be represented in the
USP.
How do you "deal with fractions" when encoding into the
USP?
Simple.
You drop fractions and round down to resolve to the integer.
This means that you CAN build a 144 tons = 48 EP power plant into a 700 ton hull using LBB5.80 ... but the
USP code for it is ... 6 ... because
6.85714286 dropping fractions and rounding down to resolve to the integer yields code: 6.
In actual USP coding this would work out like so:
XX-7XX665X-X?0000-?000?-X MCr? 700 tons
Agility=6. EP=48.
Is seeing EP=48 in a
USP stat block for a 700 ton craft ...
UNpossible?
No ... no it's not.
It might be
unexpected but it's not impossible.
It would certainly help to have "more details" about the design than what the
USP block alone will provide, but that's the province of Fluff Text™ and class history fleshing out the design of the class (and the reasoning behind the "non-standard" result that isn't a typo).
Alright, so if battle damage is taken to the power plant, what does its EP output drop down to then?
Haha! Gotcha!
Actually, no you haven't.
For the
@Grav_Moped or
@mike wightman class designs, in order generate 48 EP in a 700 ton hull, a code: 7 power plant is MANDATORY which @ TL=11 will require 147 tons and will generate 49 EP ... yielding a wasted surplus +1 EP that the design cannot make use of.
A power plant -1 damage hit would reduce the power plant from code: 7 to code: 6, at which point it will only be generating 42 EP.
Hopefully that makes sense to everyone reading this far.
We good?
For my way of dealing with the class design, in order to generate 48 EP in a 700 ton hull, a code: 6 power plant is needed which @ TL=11 will require 144 tons and will generate 48 EP ... yielding a wasted surplus of 0 EP by design.
A power plant -1 damage hit would reduce the power plant from code: 6 to code: 5, at which point it will only be generating 35 EP ... not 41 EP.
Hopefully that also makes sense to everyone who has read this far.
It's a more "complicated" way of doing things, but it doesn't suffer from issues of
Premature Optimization that can block off creative opportunities in the design of craft in
Traveller.
Your mileage may vary, of course ... depending on which end of the telescope you choose to look through.
"perfect, inviolate and immutable" 
