[shevek]

Say 1♣ is 16+ and 1♦ 0-7.

A common structure over a Standard notrump caters for strong hands,
so Stayman then 3x is forcing, transfer then 3x is GF, etc.
How do people adjust when responder is known to be weak?

For instance
1♣ - 1♦ - 1NT (16-18)

♠ Axxxx ♥x ♦Qxxx ♣xxx

If you think this hand is worth an invite (debatable), transfer then 2NT is a bit silly.
Stayman then 2♠ COULD show this.

If you agree to do that, you give up on some Garbage hands, such as
♠ Jxxxx ♥Kxxx ♦xx ♣xx

If Stayman then 2♠ invites, it's unsound to do that with this hand.
So you decide to transfer, risking the 5-2 when you have 4-4 hearts.
Seems quite close to me.

Unbalanced hands with 5 hearts are awkward.
♠ x ♥Axxxx ♦Qxxx ♣xxx

Stayman then 3♥ over 2♠ is unsound.
(However, this sequence usually a good spade raise but you don't need that if 0-7)
You can transfer then guess (probably pass), or
Stayman then hope to play 2♥ over 2♦, 2NT or 3♥ over 2♠. A bit messy.

The bigger issue is shapely hands with a 4-card major:
♠xx ♥Kxxx ♦xx ♣KTxxx

You could pass a 16-18 1NT rebid but opener could have 4 (or 5?) hearts. Easy enough to constract game hands:
♠Axx ♥QJxx ♦Axx ♣AQx

A thought is Stayman then 2M to show unbalanced 4+, mild invite.
Could play 2♥ in the 4-3. If opener prefers spades, then 2NT or 3C could end the auction.
With 4-6, Stayman then the minor works well.
♠Axxx ♥x ♦Jxxx ♣xxxx

Stayman then pass 2♦ or bid 2♠ over 2♥ to show this.
Difference here is that opener might raise 2♠, not what you want.
If this sequence is weak, responder needs to rebid 2NT with this:
♠Axxx ♥xx ♦Jxxx ♣QTx

Would be good to bid 2♠ on the way to 2NT with this, in case opener is minimum with both majors.
Need to give up on that if Stayman then a suit is a scramble.

Transfer then a suit could be invitational, so
♠ x ♥Kxxxx ♦Kxxx ♣xxx

can transfer then 3♦. Not so good with these cards but appealing with 5-5.


Views please.

[wodahs]

If you open almost all 11 point hands, and your 1NT opener is 11-14, there is no (or extremely little) need for an 'invitational' Stayman when 3rd or 4th hand opens 1NT. You are now looking for the best partial. We do this after P (P) 1NT (P); ??

2C = both majors, at least 54, opener's 2D = "no preference"
2D = any single suiter, relay to 2H (except opener can super-accept in hearts, by bidding 2S)
2M = 4M and 5+m, opener asks m with 2NT, opener bids 5-card suits up the line (hopeful .. after 2H opener bids 2S with 5=2=3=3 maybe finding responder with 3=4=5=1)
2NT = at least xx5=4
3C = at least xx4=5

Works well at finding our best partial. It doesn't answer the specific question you asked, but might be helpful in some way.

[Zelandakh]

I am not entirely sure what you mean. If you have a maximum 1♦ response (7 hcp) and partner shows 16-18, is an invite really of no use to you whatsoever? Similarly 1♣ - 1♦; 1NT - 2♣; 2♠ - 3♥ can easily show a good spade raise, exactly as it would after a 1NT opening. Perhaps you have some distribution and the hand has seriously improved from a mere 7 hcp knowing about the spade fit. You can also use this 3♥ rebid to check for a 4333 hand to try to make better decisions in choosing between 3NT and 4♠.

It does seem to me that you are developing your thinking towards a Keri style of responses here. Perhaps that is something you could look up next to see if anything there fills the remaining gaps in your ideas. There are also some other similar ideas floating around these forums, one from Justin that specifically handles the weak invite hand you are discussing.