I'm about to bust 9mil SP and run lvl 3's in a Raven.
http://ineve.net/skills/character.php?charID=805920552 Top Slots:
6 Cruise Launchers
1 Tractor
1 Heavy NOS
Mid Slots:
6 T2 Shield Extenders
Low Slots:
1 Shield Power Relay
4 T2 Power Distrobution Systems
I just upgraded to the T2 Extenders, before those I had 6 Regolith Large Extenders. I also use T2 Drones. Prior to some of my T2 improvements, this was still a solid setup for running lvl 3's and in most cases, overkill.
Unless I get stupid and aggro an entire room at once, I never have to run.
I would not reccomend this setup for lvl 4's, go with an active tank. The advantages of this setup is I lose very little time in station dinking with my rig, I get my mission and go. No loading the right rat specific resist, etc. I carry enough missiles in my bay to cover every damage type and on level 3's, mission specific drones are not much of an issue.
I don't reccomend BC's. All the the slowness, less shield, less cap, less grid, less hull, less armor. Pony up the dough for a BS and you will be happier if your doing PVE missions. BC's have their place, but if I had it to do over, I would have skipped the Ferox and gone straight to the Raven.
btw, lvl 4's are quite a bit more risky solo, even in a BS.