You've got both majors, so how about a negative double? Predictably, LHO now bids 4♦ and when it comes back to you, you can offer a choice of majors by bidding 4♥. Did you land on your feet? Hardly! You can surely make slam and possibly a grand slam. How are you getting there when partner passes 4♥? So, you're kind of obliged to bid 6♥ now.
In other words, just thinking one move ahead in the auction tells you right away that double is a bad idea. Actually, it could be even worse. Suppose partner's hand is ♠xx ♥xxx ♦AQx ♣AKxxx? He might even pass 3♦X and you might score only 500: not even compensation for game.
I've seen some abuses of negative doubles in my time, but I think this one takes the cake. The primary purpose of a negative double is a bit like Stayman: opposite a relatively balanced opener, let's see if we can find a 4-4 fit. Opener is reluctant to bid a three-card suit opposite a negative double. How many cards in the majors do you really expect partner to have here?
At my table, I bid 3♠ over 3♦ and, after my LHO predictably raised to 4♦, my partner was able to raise me to 4♠ with his Q96 holding. Roman keycard Blackwood did the rest: I found out that we had all six key cards (including the ♦A in case I wanted to bid 7NT) and I didn't really have to think too long and hard to bid the grand. But which grand? If it had been MPs, I would have probably bid 7NT. But at IMPs, you should maximize the chances of making by using your nine (hopefully) trumps.
Here's the whole hand:
The contract was lay-down. I scored six spades, five hearts, two clubs, a diamond ruff, and the ♦A. I'm kidding as that adds up to 15 so I never scored a diamond or the fifth heart.
There were five others in 7♠ (we won 12.5 IMPs on this hand), ten in 6♠, ten in a spade game, and one unfortunate fellow in 7♣ down six. To say that he (or she) was hoist by their own petard would be an understatement: South never bid either of his majors: he began with a negative double then, after his partner doubled 4♦, he chose 5♦ (which the robots interpret as showing club support).
