I've seen the ripcords advertised in the Century catalog - the ones that come in the various colors that each offer different resistance levels. Whenever I've seen a picture of someone using them, it seems they're always kicking. Would these be good for punching as well? I know that Ringside and Everlast carry similar products. Has anybody used ripcords in their training, and if so, what did you think? I'm especially interested in any feedback people have regarding using them for punching.