It will totally depend on the rockers that you're using. My Trick Flows fit beneath my valve covers with the baffle removed but the Scorpions would not.
As for the baffle... There's not reason why you can't put your own baffle into the filler neck itself. I found that a couple of the screens from a meat grinder (yes... meat grinder), placed into the filler neck about 1/4 apart, works great. I'm sure there are lots of things you could find to tack weld into place to keep the oil splash under control.