Farlsborough wrote:I've heard of people using 2 b***s should one break, although I don't know how this works having never tried it.
I find that it is worse to use 2 RB, one is plenty and if it breaks you just use the classic out "Hey, nothing's perfect." I tried using two a while back, and I forget my exact reasons, but it was a little bit too stiff and the RB flashed a little bit. Maybe I just put the second one on badly, but I personally will not be using two.
Now to the main question at hand; make sure that the RB goes into the grooves in the sides of the FC. Also make sure as Wukfit mentioned, make sure that the grooves have not been flattened out from extensive use or falling. If they are, you need a new one.
Hope that helps a little,
~David