Can GCS employ this tactic to destroy an ISD ?

[Kazuaki Shimazaki]

One can always look at Solo Command, where Stellar Web used her grav-wells as a source of realspace propulsion - more than her main engine output, apparently.

For Star Trek, one can look at Hero Worship, when a grav-well kept the E-D from even making warp 2. They were counting off the increasing gravities before Picard tried to wimp out by going to warp (and failed,) and I think the upper limit for that incident was about 1100Gs.