[benlessard]

The basic idea is that sometimes you can ask for keycards directly without making a cuebid at 4M-1.

ex S is trumps and you have made 4m cuebid (or anti-cue) 4C-4D-??

Now in a sense its a bit inneficient that these 3 auction are different ways to ask/show keycards.

4C-4D-??

4NT
4H-4NT
4H-4S-4NT

After 4D you have 4 type of hands taking into account values and H control.

min, no H ctrl =4S
max & H ctrl = 4NT
max no H cue
min but H cue

Wich of the last 2 you want under 4H is a matter of style but i prefer that 4H is slam going but deny a H cue.

My idea is to use 4H both as a turbo bid or as a cue ask.

4D--??

4H = odd number of keycards or ask for H cue or some void hands if possible
4S= min and no H control/ signoff
4NT= EVEN but no Q of trumps
5C = even + Q of trumps + K!C (unless you play denial for kings)
5D = even + Q of trumps + !DK (no !CK,unless you play denial for kings)
5H = even + Q of trumps etc...

Its even possible to switch the cue meaning of 4H/4S.

4D--??
4H = to signoff in 4S or odd number of keycards
4S = last train (im my case foward going but no H control)
4NT+ = even etc...

Obviously over a 4C cuebid the same principle applies. Going to 4NT+ directly = even keyc, temporizing is normal cue or odd number of keycards.

[Zelandakh]

Assuming 4♦ bidder is the less-described hand (Captain):

... - 4♣ - 4♦
==
4♥ = "I have a diamond control, do you have a heart control?"
... - 4♠ = no heart control
... - ... - 4NT = RKCB
... - 4NT+ = heart control + appropriate key card response
4♠ = no diamond control
4NT = whatever you want it to be, probably either replacing 5♥ as XRKCB with a heart void or just keeping it as RKCB without any interest in the heart position
5♣♦♥ = XRKCB with red suit controls

Again it is a question of philosophy as to how one uses the extra space. LTTC is only one option here and one should not forget that S/F 3NT has already been bypassed so we ought to know if we are in the slam zone or not:
P1: "We have enough for slam if we are not off 2 quick tricks."
P2: "Great, let's check on that."
P1: "We are not off 2 QTs but I am not sure about the general strength any more so here's a slam invite again just in case."

or

P1: "I would like to invite a slam."
P2: "I accept your invite."
P1: "I am not so sure, let me invite again just in case."

[benlessard]

For the LTTC I see it this way.

4C is Serious.
4C-??

Using show method
with cue in both suit and extras you can directly go for keycards.

With a cue in H but none in D you bid 4H

But what about 4D ?

1- cue in D no cue in H
2- D cue, may also have H cue if minimum. Cue in both D&H & extras can directly or delayed ask for keycards anyway.

AFAIK 2 is much more popular than 1.

So that why 4C-4D-4H as showing extras but no H control is very good even with a serious sequence.

If 4D would show a D but deny H.
Than 4H would be min but with H control.

Playing 4H as may or may not have H control is simply inferior.

As for making a direct 4NT vs delayed 4NT its hard to know whats the best meaning to divide but so far im very impressed on the skip turbo method.

[benlessard]

If its 4D--??

where 4D is show and serious.

With cue in both rounded and extras you can rkc (delayed or not).
Without a c cue you simply bid 4S.

So you have 2 cases, club cue no H cue.

clubs cue may have H cue but min.


4H = show club but may or may not deny H.

For simplicity and symmetry i prefer that 4H deny the H cue (unless fake ask)