disk size has nothing to do with it. Here is some text from Franks site. hope ya dont mind me posting it here................
30-03-2006 At Daniel Wehrli, a well known breeder from Switzerland, pups have bin born from Pearl and Reticulate stingrays. About the last one I want to tell some more. The mother Potamotrygon Reticulate had a disk size of only 6 inch. She had 3 pups with a disk size of 21/2 inch and a total length of 6 inch. It is unbelievable that such a small mother animal can produce 3 pups of that size my compliments. When you compare the Pearl pics with the Reticulate pics you see that the Retics have a very long tale compared to their disk size, is is twice the length of the disk. The pictures below are from Daniel Wehrli the owner and breeder of these beautiful animals.