Nope, but my Urologist once told me that I might consider doing this. Not to prevent retraction though but to prevent ( don t know the right term in english ) the testicle from spinning ( 180 or even worse 360' degrees ) due to abrupt movement. I do martial arts and have a rather large ballsack. I had one of my testicles twisted a couple of times and this can be very dangerous and the testicle might even die from blood restriction. Now I just use the special ball protection used for real combat all the time during training, which keeps the whole thing compact and prevents such injuries.
It\'s called a torsion and involves the spermatic cord and essentially \"chokes\" your testis. I\'ve had one before and it was very painful. After some gentle massage, I was freed from my pain. There has been no recurrence for me.