I have never tied cock and balls, but I have tied tits, I should imagine the same respect must be shown to the male part ,meaning always be conscious of how tight you tie it. Blood flow is important, and if you do have it tight enough to stop blood flow then they must be released at least every 15mins,so that a blood supply can get to your dick and balls. But always bear in mind how tight you tie it because internal damage can be caused to veins,muscle,or nerve endings. Have fun experimenting.