GekiChopper is not the 6th ranger of the team - this is proven by Gokaiger. See Ranger_Keys_(Super_Sentai)#Gokai_Silver.27s_Ranger_Keys for a list of the 6th rangers. I also had to reduce your note about Gou - he came after the first 3, but his connection therein has nothing to do with a 6th Ranger at all.
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