Although I know why fossy is so angry and upset at his current situation 'slapping a van' would not be my advice.
Didn't we have an incident on here where a cammer did just that and got thumped?
Then completely denied the 'slap' had taken place?
I generally stay calm on the road but occasionally even I want to tell a driver exactly what I think of their driving, just the other night I had a guy in a huge Mercedes squeeze me into the kerb after going for an ill judged overtake (in a narrow 20mph zone) and then driving off despite my obvious displeasure at him, caught him up 200 yards later at the lights and had my say.
Needless to say he couldn't care less and told me to 'behave myself'
Got to try not to let these things linger as it can spoil the ride, or even future rides too.