Sorry for the slow response.
The "Set with viewer" option is not available for Tile Set Definitions due
to the awkward limitation at the moment where it is not possible to create a
runtime map instance off of a Tile Set Definition (that we need in order to
be able to present an interactive map viewer). This is a MapGuide Server
level limitation. The only practical workaround would be to set up some
placeholder tiled map definition against the same set of layers and
copy/paste the custom bbox using this feature over to your tile set.
Now having said that, I have discovered a bug that prevents MgCooker from
properly calculating the meters-per-unit value for a selected Tile Set.
Having this set is important, as a bad or incorrect MPU can wildly throw off
the calculated total number of tiles that MgCooker needs to generate
(override bounds or not).
I've logged an issue on that matter:
View this message in context: http://osgeo-org.1560.x6.nabble.com/TileSetDefinition-Override-Bounds-feature-in-MgCooker-tp5318041p5319948.html
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