I wouldn't uneccessary overcomplicate this. Maybe just something like the lightmap resolution preview in the unreal engine. There is basically no need to define the perfect resolution. This is up to the user to decide. Just a visual helper to view the resolution. It probabely would be even better to make this not a render element but a viewport feature within max.
Edit:
Example: Link below doesn' t work.
http://i.imgur.com/mStJcIH.png
Edit:
Example: Link below doesn' t work.
http://i.imgur.com/mStJcIH.png
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