In the front, the 50 Rep bra pretty much fully hides underneath the Flow Y except for the straps. The bras overlap each other in the front of the armpit. The 50 Rep has a deeper cleavage (i.e., dips lower) than the No Limit.
The 50 Rep is a little more obvious in the back but I think it's livable when layering black on black. When I wear my Aruba No Limit I will use another Flow Y bra underneath. I wanted to try it with an Aruba 50 Rep when I was at the store today but they didn't have one.
This is a bit blurry but I think you can see the edges of the No Limit on top of the 50 Rep in this photo.
Hope this helps and forgive my non-model like physique and dry skin. ;-)