New DSIP rule to cope with two-suited bids

In the DSIP rule summary, I state that doubles after a two-suited bid (by either side) are for penalties.  The one noted exception is that when partner makes a two-suited bid and one of the suits is unknown, an immediate double asks partner to bid the unknown suit.

When they make a two-suited bid, the situation is slightly different.  Whether we know both suits or not, we don't know which suit they are going to settle in.  I propose that a delayed double after they make a two-suited bid is for takeout of the suit they have now bid.  This should not be confused with a delayed double of a (known) suit, which is always for penalty.

Here's an example of a hand where a delayed double would have worked better.  Partner opened 1NT (12-14) and RHO bid 2NT for the minors.  None were vulnerable and I held the following hand: ♠xxxx ♥Kxxx ♦x ♣KQxx..  I wanted to compete and/or to suggest a possible penalty so I doubled.  Partner doubled the takeout to 3♦ and they made 5 (most probably I could have saved a trick but I thought I was squeezed).  We lost 11 imps on the board. Obviously, I didn't have enough hcp to suggest a penalty double.

What I perhaps needed to do was to pass over 2NT and then double when 3♦ came around to me.  Even then it's a questionable action because my club holding won't be very useful.  But I think we'd have done better than -670, assuming partner takes it out to his four-card major.