String of suggestions.

[Eric.B]

Which is true, and it would be more understandable if it were random i.e. high skill (slightly better with slight variance), mid.. (about the same as expected), low (results are randomly lower than expected).

But then that would make it not random, as you'd always know that your estimates are undershot because your skill ratings are low or overshot because your skill ratings are high. On top of this your estimations would never be right. Even the most poorly skilled people can make a good estimation sometimes.

The randomness to estimated values works like this: The higher skill is the less variance of randomness from the real value. If you have low skill you could be anywhere between 20% off plus or minus. Including perfectly correct. If you have high skill you could be between 2% off plus or minus. Including perfectly correct. (Note percentage numbers are made up, I'm not going to go look at the code to see what they are exactly.)

However it's a consistent and predictable error 45 rated engine gives 2 1/2 stars in design panel and when the model is completed the same chassis/engine etc.. has the same rating just 1/2 a star less.

Stars have nothing to do with anything, they're just graphical representations of the rating numbers. Because some people hate numbers. So if that occurs (and I haven't checked it out yet) it's merely due to the conditional checks against the ratings to display the number of stars. The only thing that matters is the numbered rating.

Other things cost is sometimes higher or lower. An engine I made to be $125 turns out to cost 126. However for the most part its consistent what you designed is what you get.

Again, this is due to randomness variations of your estimations. You actually designed a $126 engine. Your skill rating however showed you it would be a $125 engine. As the prices of the engines go up, the difference should be more noticeable.

just make your engine 25/45 rated engine rate 46 or 26 it'll keep it's stars

Again, stars have nothing to do with anything. If 45 give you 2 stars on one thing but 2.5 on the other, and if you have 46 rating and have 2.5 on both. Then it's simply because in one conditional statement to display stars I have ">" and the other I have ">="