Lots of NHRA stockers running near or in the 9's with a stock pan, but are also using baffles, crank scrapers and mesh type windage trays. So no, it's not necessary to have a real deep pan; just get the oil back downstairs as fast as you can and away from or off the crank. I've heard over the years that many stocker guys toss the stock windage tray as it doesn't drain fast enough and instead use the mesh type. Grinding/smoothing drain back holes for casting flash and smoothing oil returns in the head and valley can't hurt either. A valley tray also helps keep the oil off the bottom of the intake and redirects any splash from the cam back downstairs.