my irons are D-2 titleist zm but I've got a couple strips of lead tape on all of them so they may or may not be a different swing weight.
I may lose a fraction of club head speed, but in exchange for being able to feel the club head I find it is a worthy trade.
I see so many players swing too fast with these lightweight clubs most are making now, I don't see how they can control a club head that is as light as styrofoam. Usually they don't.
They can have fun with the fly swatters, I'll take the sledgehammer feeling any day.
I am young (27) athletic and healthy if that makes a difference in how this opinion is perceived.