Time for today's brake related question...Disc/drum combo

I have upgraded to front discs on my Dart, and original 9" drum car. Also added 10" drums in the rear.

I have upgraded to the MP lightweight master cylinder.

Question: Do I need an adjustable proportioning valve?? Some say yes, others no. I am being told with this MC, I don't. Anyone have any real world experience either way?

My one experience with this was once I added OE disc brakes to the front of a 73 Ebody (race only) and no stopping issues what-so-ever with out one.