Seems to me that the OP is making this bike into something it never was intended to be, not wrong but not "Great Again" either.

Stem and post weight is a funny thing. Both being fairly high up off the ground contribute to what I'll call "rocking weight", the feel of how easy it is to rock the bike back and forth while standing. Yet as otherwise stationary weight they do little to change efficiency. I'll add that I have seen far more riders fall from broken posts, stems and bars then I've had riders tell me that they only got up that big hill because their post was 58 grams lighter. There's a reason that most stems are solid, as example, and a reason that some of the hollow stems are called "death stems".

What I have done with common parts is to cut off any excess. For a post that's any of it's length after about 3" of seat tube insertion. For bars that's the last bit of the drops, I never go down there anyway. But the stem I leave stock, my helmet lacks a face guard. Andy