From everything i've seen about shipbuilding...this stratagy is everywhere.
There are some modifications you could do depending on your style
i never actually tried with just 100 space left, but i assume you can get better HP and attack since you will have more energy.
The ships i build (and i learned this from Ars, and everyone i talked to) have 1000 free space after the powercore to use less energy on the upgrades
Borg, the only question i have for you is, is weight important, or is the extra energy (which might not be that much more) sufficient to get a better upgrade for less weight, or are they both the same?