So I am trying to replace my tube in my 800 and all is going to plan except: I have a little rubber stopper left over. When I took the old tube out, this stopper was infront of the top of the tube on the board in the groove. However, isn't it supposed to sit ON Top of the tube to hold it in place to the board? This would make more sense to me, or should I just put it back the way I found it? Ideas anyone?