I have used both, its all about getting it thin and properly prepping the ear. National titles have been won with bondo and commercial ear liners. Today most competition pieces use ear liners but still to this day one of the very best taxidermist uses bondo. I just found that out and I would have sworn he used liners.
However if you notice a mount with ears busted out at the top or curled over and oddly shaped, likely bondo. Like anything its all about how you use it.
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