The (cheaper) repops tend to split in the corners of the rectangular hole. This can be solved by first cleaning any molding residue from the inside with rubbing alcohol. Take a piece of plastic, metal or what have you, cut a plug the size of the hole, then apply a mold release of some sort. Place into the hole then apply a quantity of GOOP (black) and let it sit upside down for at least 24 hours until fully cured. Pull the plug and you're done. Another way I did this was to actually cut a piece of plastic that fits inside and GOOP that in as described above. This does not affect the shifting pattern. Since doing this, I have not had that problem, just splitting in other areas. The "rubber" is not what it used to be!!
