I like to sprinkle some sea salt over the deviled eggs just before I serve. If you sprinkle the salt too soon, it will start to extract liquid from the radishes and create little puddles. So wait until the very end if you sprinkle salt on top.
Feel free to add a little more mayonnaise if the filling is too dry for you.
The product known as mango chutney in the West is not something I ever saw sold in stores in India. The closest thing to it would be what we call morabbo in Gujarati, which is a like a jam made with mangoes and spices..
This recipe is adapted from Epicurious.com