As mentioned above, I'm following Waldronate's instructions in the link I posted.

So, to your questions, yes. In wilbur, I am using Surface>>Map Info to set World coordinates to to -90, -180, 180, 90. Then I flip. Then I am using Filter>>Mathematical>>Span to set min and max height ranges.

FTR still does not recognize it.

Thoughts? Waldronate, are you out there? Do you have any wisdom to share on this?