bass playing, esp in slapping, is a relatively new technique. i suppose there isn't really right or wrong way per se, only some of the advices or ways ppl have experimented and thought more ergonimical or efficient. While checking out how other dudes are doing it, one can actually take it further, find the way tat's the most comfortable for himself, or even create sth new, just like victor Wooten's double thumping!