I second Aodha's claims here. I've spent long stretches of my life as a vigilante, and even with a moderate kill-count on members of pirate corps who were not outlaws, your sec-status drops pretty sharply, low-sec ratting get's a slow return. If you are going to go for PVP in low-sec being pirates or quasi pirates high-sec will be denied you very soon, I was down to -3.5 very fast in a moderately effective period, and I usually did not pod anyone at all, even if I vere able to do so.
To be more constructive, for a small-size corporation who wants to get more effective in PVP I'd say you should gear up in affordable ships, like T2 fitted cruisers and BC's coupled with the odd BS, and dec smaller but more combat-minded corps. don't dec larger entities that only 'fight' when they can effectively blob you, or more industry minded corps. With them, you will either scare them into station in a few days or hours, and not learn a thing, or you will keep poping poorly-fitted and in-experienced people. When the fight is next to non-existant or increadibly one-sided you usually don't learn anything usefull.
Also, war-decs allow you to contain the conflict a lot better, you lose no security rating and apart from any neutral helpers on either side things stay pretty simple between you. Say, a less-than-20 vs another less-than-20 corp, and you got a very 'balanced' war, in terms of numbers. All you need then is for both sides to be willing to risk their virtual assets for some fun. Even in today's EVE, that is not an impossible demand.