when using a man to man defense how often and in what situations do you use double teams???

lately I've been trying them out in situations where one player takes the bulk of the opponent's threes - I'll sag to a -2 or -3 if my adjacent defenders have enough spd (with 10 pts below or over) and I'll double that 3 pt shooter if leading scorer just in case he burns my minus. If the 3 pt shooter has poor def or I have a significant spd advantage with an offensive player I'll up my distro vs him too to get him in foul trouble...

I will double team if a player has 25% or more of the offensive contribution and if he has poor passing/a poor FG%.