TiddlyMap raster question

[Ed Heil]

I'm going to use TiddlyMap to key a map (for a roleplaying game) -- put in the map and then use the raster feature to place tiddlers in specific locations on the map, so I can click on the place on the map and pull up the tiddler which describes what is there.

Essentially I"m using it as if it were an HTML imagemap.  Arguably the power of TiddlyMap is complete overkill for this but whatevs, it works!

I need the raster feature to be able to place tiddlers on the map at the appropriate locations, but the map I'm using *already* has a grid on it, and having it and the rasters on there together is weird. 

I'm wondering if there's a way to turn the visible grid off when using the raster feature, so that you can place tiddlers in specific places on the background image, without that visual indication of the grid?