Yes, the stock length chain will work for both 47 and 50 tooth rear sprockets. Here is the 47/50 dual sprocket setup that I ran until I switched to 47/55 which requires the addition/deletion of a short chain segment.
I have never actually measured the slack. I have just learned to set it looser than I think it should be and then double check it again after I am sitting on the bike. This process seems to be working for me.So that's how it looks with the dual set-up Hmmmmm... How much slack do you run on the chain????? Yours appears to be much tighter than mine.. OMM.