If I had to do this again I wouldn’t use stainless steel because it’s harder than my HF drill bits, and I’d make the door smaller and farther forward. When the door opens it hits the oil pump so it only opens about a 1/4" (Credit to Rich Bratton for figuring that out). My still works because the door and openings are pretty big so enough oil flows out of the left baffle to be useful. This oil pan has had 9 track days as of this writing and no OP hiccups in hard turns.
Note that there is a plastic ix part for this exact purpose. It’s part #2 here:
http://www.realoem.com/bmw/showparts.do?model=1293&mospid=47311&btnr=11_1890&hg=11&fg=10
If you focus on the pic you’ll think “how can that work”. Ignore the pic. If you want an easy door solution just call up the dealer and order that part. Cut off the curved part and you’ve an instant left-side oil baffle door.