10% of 400-500m is still only 40-50m, so it's not that much closer, is it?
But still, if I push the limits way closer than that (say close enough to start the stabilizers at 5% efficiency), the amount of stabilizers rivals major systems in the build (I tested this with a 1mill e/s reactor, and had to add like 88k of stabilizers in order to attain 100% stability on the reactor, the only system in the build at a comparable blockcount was the salvage array coming in at approximately 52k blocks). The further out you go from the reactor, the better, because it lowers the amount of stabilizers an incrases their efficiency, but it might not work for small or compact builds that actually do need a lot of power to start with.
So it becomes a struggle, you need to decide what power you need to run the ship, you need to decide what the dimensions need to be, and you need to decide where to put your stabilizers just to get the most out of the reactor setup, and you may still end up with a ship that is broken and not what you wanted.
Why do I get the feeling that the devs wanted to simplify the power system, but ended up making it even more of a hassle to build stuff because of all the restrictions. Furthermore, this system favors hull-first builds, because its easier to build power into an empty hull as you already have set dimensions to work with. It's harder to build systems first, because then you need to figure out how to fit the hull around the systems you've built, in order to make a ship out of a clump of systems.