I'm a little late to this discussion, but I thought I would add a method from the 1960's, part of the Flint-Pender system (Tiger Bridge, 1970). It's short, so I might as well quote the whole thing: "Responding to three clubs or three diamonds is often difficult because so much may depend on whether the opener's suit will run for seven tricks opposite a doubleton honor. Partner opens three diamonds and you hold: AQx Kxxxx Kx Kxx. Three notrump could be a laydown or preposterous, depending on partner's diamonds. "Our solution is to treat three of the next ranking suit as a conventional inquiry. With two top honors in his long suit, opener rebids three spades; with support for the relay suit, three notrump; with neither he repeats the suit. On the hand above, responder bids three hearts. "Opener holds: xx QJx AJ10xxxx x: bid 3NT. x xx QJ109xxx QJx: bid 4D. xx xx AQxxxxx xx: bid 3S. "Should opener happen to have both support for the relay suit and top honors in his own suit, he should give precedence to the latter and bid three spades, as he will have the opportunity of disclosing his support on the next round." This just shows that somebody was working on this problem 40-odd years ago. T. L. Goodwin