[firmit]

Normally 1m-1H-2S is strong jump shift, GF 5-4 (18)19-21 or so.

But is this really recessary?
I play 11-19hp and as long as 1S is F1, I see no reason to jump:
1m-1H-1S promising unbalanced hand, limited upto a 2C strong opening.

Now, 1m-1H-2S is preserved as a splinter jump GI+ showing and denying certain handtypes, and is no longer a "dual"-type bid which shows either a strong reverse or a splinter - the type which nobody approved

What is played among experts? I know of several in Norway that uses sjs/splinter dual, but what is streamline?

[FrancesHinden]

Many people do not wish to play 1m - 1H - 1S as forcing. This is often the case for those who respond very light, particularly to a potentially short 1m opening. If they consider Jxx Kxxxx xxxx x a 1H response to 1C, they want to be able to pass a 1S rebid.

Once you decide that you want 1S to be non-forcing, you need 2S to show a very strong hand.

However, there are some pairs here in England that play 1m-1H-1S as forcing. In one partnership I do so. As you say, that frees up the 2S bid for other purposes, but we don't use it the way you suggest. It depends on the minor suit opened, but we play

1C - 1H - 2S as either
i) 3-6 in hearts and clubs, invitational (the typical bridge world 'death' hand e.g. x Axx Kxx AKJxxx)
ii) 4 hearts, spade singleton (1C - 1H - 3S shows a spade void)
iii) 18-19 balanced with 4 hearts

2NT asks, then
1C - 1H - 2S - 2NT -
3C = 3-6 hearts & clubs, NF
3D = 18-19 bal with 4 hearts, F3H
3H = spade singleton, NF
3S = spade singleton FG
3NT = 18-19 bal with 4 hearts, prepared to play in game
4C = 3-7 in hearts & clubs

Responder doesn't have to bid 2NT but usually will(!)

1D - 1H - 2S is different, as 1C - 1H - 3D is available as a mini-splinter, but 1D - 1H - 3C is strong, so

1D - 1H - 2S - 2NT
3C = 18-19 balanced
3D = 3-6 in the reds, invitational
3H = spade mini-splinter
3S = FG spade singleton

So 1D - 1H - 3H is either a club mini-splinter or 2452
1m - 1H - 4H is 5422

[ArtK78]

If you read Granovetter's magazine, you will find that he argues that the 1♠ rebid may be up to 19 or 20 HCP, but it is STILL NOT FORCING. The argument is that if partner cannot take a second call, it is likely that you don't belong in game.

He gives a number of examples showing how a 1♠ rebid on a very strong hand would have avoided a poor game, even when responder did not stretch to respond to the opening bid.

In my experience, I have seen many cases in which opener has insisted on forcing to game on a 19 count after partner's one level response and it worked out badly.

In standard bidding, 1x-1y-1z is not forcing. One should consider rebidding 1z even with a very good hand, since game may not be great opposite a lot of minimum (not sub-minimum) responses.