Any easy way to increase max planet class?

There are mods available that allow multiple terraforming of tiles.

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Yes, but I have been reading here and there is a lot of talk about most or all mods pre-Crusade being broken...

There's an enhanced terraforming mod by BuckGodot that gives you repeatable terraforming projects that require resources to build.  The original mod won't work on Crusade, but if you look at the May 4th post by me you'll find a link to a version that does work on Crusade.

Edit: I've been having trouble getting the link above to work.  If it doesn't work, try this: https://forums.galciv3.com/469459/page/1/

There are several files that impact planet number and class

A quick and simple way to increase planet class is to mod (must be a mod not a change to core came file) GalCiv3MapDefs.xml

e.g.
    <DefaultPlanetClassSelect>
      <MinPlanetClass>6</MinPlanetClass>   increase
      <MaxPlanetClass>10</MaxPlanetClass>  increase
      <Weight>15</Weight>      % distribution

There are several sections ans the total <Weight> must - 100.  So another way is to decrease the weight of the smaller class entries and increase the larger ones

hope that helps

Yeah! Thank you guys! That's the info I was looking for!

PlanetTraitDefs.xml

change the min and max for planets like so

  <PlanetTrait>

    <InternalName>DesertWorld</InternalName>

    <DisplayName>DesertWorld_Name</DisplayName>

    <Description>DesertWorld_Dec</Description>

    <RelativeWeight>10</RelativeWeight>

    <PlanetClassSelect>

      <MinPlanetClass>50</MinPlanetClass>

      <MaxPlanetClass>60</MaxPlanetClass>

      <Weight>100</Weight>

    </PlanetClassSelect>