This scheme is intended to right-side everything,
minimse information leakage about opener's hand,
and not be too forgettable
(though it hasn't always succeeded in that last objective).
There are two downsides that I'm aware of:
it doesn't allow many invitational sequences,
and the bids to show both minors wrongside 3NT.
There are a few bids that aren't used,
but could be - eg 2♠ followed by 3♥.
We decided that it was better to limit the number of meanings for each first-round action rather than try to cram everything in.
2♥ = 4+ spades, then after 2♠
- 2NT doesn't exist
- 3♣ = 4 spades, longer minor
- 3♦ = 5 spades, 4+ clubs
- 3♥ = 5 spades, 4+ diamonds
- 3♠ = 3NT bid with 4 spades
2♠ = to play 2NT OR 4+ hearts, then after 2NT
- 3♣ = 4 hearts, longer minor
- 3♦ = 5 hearts, 4+ clubs OR signoff in 3♥
- 3♥ doesn't exist
- 3♠ = 5 hearts, 4+ diamonds
- 3NT = 3NT bid with 4 hearts
2NT = forces 3♣, then
- Pass = signoff
- 3♦ = balanced slam try
- 3♥/♠ = minor one-suiter
- 3NT = both minors, some specified shape
3♣ = both majors, 4-4 or longer (opener responds as to Stayman)
3♦/♥ = transfer - game-invitational, 5332 slam try, or 1-suited slam try
3♠ = signoff in 3NT OR both minors, slam try
3NT = both minors, some other specified shape
After 2♦-2M; completion-3♣, opener can bid 3M to agree the major, or 3♦ to ask for the minor.
In reply to the ask, responder has two bids below 3NT that don't wongside anything.
The lowe shows clubs, and the higher shows diamonds.
That sounds more complicated than it is.
I've just typed this from memory;
now I'm going to compare it with the notes.
That might be a worrying experience.
Edit: a simple improvement
(which I've only just thought of, for some reason),
is to play 2♥-2♠-2NT as a balanced slam try,
and 2NT-3♣-3♦ as a natural invitation.