That could likely fix the base movement, but theoretically though, it should move normally on it's own. For example, if it were just a furry tentacle, it would have no base to connect to (though obviously that would be weird and unlikely, but just as a hypothetical case). I get what you're saying about the skin weights…
You answered it yourself: Skin the base of the tail to the same bone as the area it should stick to (pelvis bone?) I'm no skinning expert and don't know much about xgen, that said, in some cases either skinning a proxy mesh and transferring the skin weights to complex geometry or transferring weights of base mesh to…
I have a furred tail GEO for a character, but when I manipulate the joints for animation, it moves the base away from the model. So ideally, I'd like to lock the perimeter of the base in place so that it will not move regardless of what else moves around it. Although, now upon having said that aloud, I realize the error in…