So I've been engineering my ass off. Well, not literally, you know what I mean. That would look funny and be hard to explain...

G5 thermal vent, errr,

When you are nearing completion of a grade and not quite maxxed, just a few percent from completed, and you've unlocked the next grade, what do you do? If I go to the next grade without completing the lower one am I leaving some performance on the table? It's small, I know, but I want to know if it is not all it could have been. I realize I may be using precious mats for a tiny gain, but once done I would rather have spent more for the most gain, than a little less for a little less.

Or does the next grade fill out the rest of the lower grade so to speak? I'm assuming I guess, that grade 3 for example builds on what was reached with grade 2. Or maybe it's just from base level and grade 3 is grade 3, regardless of what you got out of grade 2. Am I making sense?