my brother use to tear his all up, but it was because during his approach he would sort of "twist" his right foot on his 2nd step (using 5 step delivery) not sure if you do the same but my guess would be you're doing something similar. I've had my SST 5's for over 3 years and the tip is sort of wearing off some, but no tears and they have plenty of life left.
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Stu in Texas