Right now, the "Dense" race trait does not actually give extra mass to use on ships.  The reason is that the 4 versions of the trait are currently written like this:

<RaceTrait>
<InternalName>Dense1</InternalName>
<DisplayName>Dense1_Name</DisplayName>
<Description>Dense1_Desc</Description>
<Mod>
<EffectType>MassCap</EffectType>
<Scope>Global</Scope>
<Target>
<TargetType>Colony</TargetType>
</Target>
<BonusType>Multiplier</BonusType>
<Value>0.25</Value>
</Mod>
</RaceTrait>

When they should be written like this:

<RaceTrait>
<InternalName>Dense1</InternalName>
<DisplayName>Dense1_Name</DisplayName>
<Description>Dense1_Desc</Description>
<Mod>
<EffectType>MassCap</EffectType>
<Scope>Global</Scope>
<Target>
<TargetType>Ship</TargetType>
</Target>
<BonusType>Multiplier</BonusType>
<Value>0.25</Value>
</Mod>
</RaceTrait>

Once I made that correction to TargetType, the trait worked fine.