What I've found out about HU is that most players are spewtards and will put people on too bluffy of a range, even if you haven't bluffed the entire match. Then what I've also notice is the 1% of the time a player realizes your just a nit who doesn't bluff, he'll either leave the table or tilt bluff because he knows he has to bluff you to win but he can't take his mouse off the bet button.

Summary: Play super tight in a HU match with the way the games are right now, if opponent starts to adjust only then loosen up.