Sadly 50mm butt rings are a current fashion that most of us simply don't need, like, to be honest 3.25lb test curve rods.
Unless you can really push a rod to its limit and maximum cast, then even with Big Pits, 50mm rings are a waste of time. In fact, in some cases, they can make your casting worse, dependant on how the line comes off the reels.
My SP's and NG's both had 40mm butt rings, and with both and Big Pits, I could cast over 100 metres. I used Shimano 10000 size baitrunners on the NG's and due to line capacity and lay, I could only hit 90metres! No need for a 50mm butt ring on that i'm sure.
Personally I would go with 40mm butt rings, but as said that is my choice.