On my LRF when i am demanding a Corporate Trader drop his goods, sometimes he F1's, as soon as i see the "cloaking" i open fire and blow up his ship fast.
9 / 10 i get him and he comes back several minutes later, one time i got one with a Codename and he cussed up a storm when an AU and i blew him up, sent me all sorts of hatemail and stuff, we gave him fair warning but he decided that an F1 was a good idea.
So i say show no mercy to F1ers, blow their ships up as soon as they try cloaking and feel better about yourselves.