Inverted Minor Raise: How Weak is “Weak”

Ken from Norfolk writes:

A question arose recently in play; to wit: if I play inverted minors how weak is weak?  I was told by the opposition that it is less than 6.  I had assume it was 6-9 as it ‘inverted’ the standard.  The standard bid is 1D-2D=6-9 and  1D-3D= 10-11.  I looked into a number of sites on the internet and found a lack of consistency.  What is the ‘correct range?” Is is subject to partnership agreement?  For what it is worth my opponent said with 0-5 bid 3D; with 6-9 bid 1NT and 10+ bid 2D.  Off with interference!  you agree?

Hi Ken.  I agree that there are a variety of ways to play it.  My personal preference is “less than a limit raise, not suicidal”, i.e. don’t do it with very few HCP if you’re vulnerable.  You need to work this out with your partner.  Your opponent’s suggestion is one way to do it, except that there are some hands in the 6-9 range with a singleton in a major and 5 card support for your partner where I would make the inverted raise and not bid NT.  It’s also easier if your partner opens 1C, as you can occasionally temporize with a 1D bid.

Here’s what Max Hardy wrote in his “Two Over One Game Force” book, page 51:
“The strength required is that of a normal response, about a good five to a bad nine points, but the more cards responder holds in opener’s suit the more he should be inclined to respond preemptively even with less in high cards.”
That looks like my “Less than a limit raise, not suicidal” opinion.