I'm looking for some clarity regarding the traits of SCX vs. DDX and RX.
From page 6 of the rules in Section 4.2:
When X is added to the end of a type it means that a non-advanced unit of that type may not be upgraded to the X version. For example: DDX and RX. See the rules under the SCX for a partial exception to this.
Here's section 4.8 discussing the SCXs:
When AC 3 is researched, the player may build the ScoutX Group (SCX #7). This acts as a normal Scout (SC) counter in every way, although it must be equipped with a Movement Technology 3 levels higher than the player has researched (to a maximum of Move 7). The original six SC Counters may still be used but the SCs in them may not be upgraded to SCXs. Until Move 7 is research SCXs must be new builds.
If the player has Move 7, the SCX #7 group confers no additional benefit and can be combined with the other groups normally.
So what is the partial exception that 4.2 mentions? I see that 4.8 says that the SCX group can be combined with standard Scouts once you have researched Move 7 since they are identical builds at that point... Is that the exception mentioned in 4.2?
Also, note the bold part in 4.8 about SCXs needing to be new builds... I'm not sure what that means.
Since I'm working on the consolidated rule book I was hoping to work it more clearly.