This is an incredibly bad idea in low cat races - you never know who's going to freak out and cause an accident. You should NEVER deliberately touch someone in a 4/5 race. If you really are a much better pack handler then the rest, lone squirrels won't squeeze you. As for changing lines in corners, you just have to expect that. Touching some n00b who's freaked out and cornering badly already isn't going to make him correct his line, and it could be a recipe for disaster. And furthermore, touching other riders deliberately is against the rules. Keep your hands to yourself.