The opponents opened 1NT

[helene_t]

DONT doesn't disturb that much. Half of your two-suited overcalls include clubs which means that with all your non-spades one-suiters, and half of your two-suiters, you either help them or make no difference to their NT structure. Even the 2♥ overcall doesn't disturb them much as they are unlikely to want to use stayman or major suit transfers when you hold both majors. You might in fact help them steering clear of a 4-4 fit in a major when you tell them that suit will break 4-1 or 5-0. OK, the same is true for Landy but with Landy at least you can stop in 2♣ when partner has long clubs, and partner can ask for your longer major, and you can bid hearts when you have a one-suiter with hearts.

 

Not being able to show your major suit when you have a M+m two-suiter is not great either. Not to mention not being able show your 1-suiter is not great either.

 

Partner will miss some opportunities to compete to the 3-level because he doesn't know you major suit.

 

DONT is ok when you are w/w at matchpoints and want to compete over their 1NT as often as possible. But I wouldn't want to play a convention that only applied in that situation.