In the end, after discussions in the GOUT Film Grain thread, I only used a very subtle degrainer - just enough to "take the edge off" the grain present in the GOUT video.
There are still issues with near-horizontal edges and loss of vertical detail, as well as the smearing and trails from the DVNR process. These defects can only be fixed by returning to pre-THX laserdisc sources, or a colour-corrected and "de-specialed" SE/DVD/HDTV source.