If we take the gravity well definition to its absolute conclusion then you'd never be able to use FTL if you're within 100AU of any star.

I've been operating under the loose assumptions that:
[list][*]orbital space gets increasingly cluttered stretching from geostationary all the way down to the karman line and relativistic collisions become increasingly likely ...
[*]subspace becomes increasingly turbulent as you get closer to a large mass object, becoming dangerous to traverse ...
[*]The Ashtar fortress a Agdemnar is throwing off heavier subspace disturbances than usual, increasing the hazard zone on that hemisphere.[/list]

It thus becomes a bad idea to jump inside of geostationary for any developed world (without going through space traffic control), and basically impossible to jump in closer than ~4-5 planetary radii (unless the goal is to smack into the planet and be annihilated, or be uncontrollably slingshotted halfway across the star system).

I'm also playing a bit fast & loose with it because in-system warp is technically slower than light, due to the primary FTL system I wrote being hard stopped all the way out at termination shock.