[gwnn]

(the following is in the context of 1C=11+ natural or 11-13 bal.)

I think I read first on BBF about

1C-p-2D* = (very) weak jump shift in a major or strong jump shift in a major.

Does this work? I assume opener generally bids 2H/2S and responder clarifies his hand. Is it overloaded though? I'm afraid that responder with the strong hand might run out of room.

[Quantumcat]

You can make 2♦ show hearts and 2♥ show spades, then opener is more informed and there is always more room (opener won't take up space and less hands to show)

I play 2♦ over 1♣ as 0-4 HCP single suited hearts or gameforce single suited or 5+ hearts 4+ clubs. 1♣ can be strong balanced or unlimited 14+ HCP natural. Opener bids 2♥ if he is happy playing in 2♥ opposite the very weak hand, or 2♠ if he has at least an invitation opposite the weak hand.

Then the responder relays:
2♠ = strong single suited
2NT = 5+/5+ ♥/♣
3♣ = short ♦, 5 hearts 4 clubs
3♦ = 2524
3♥ = short ♠ 5 hearts 4 clubs

If shortness has not been shown (2♠ or 2NT) next relay is for shortness, otherwise then controls, then the rest of our relay stuff.

[Free]

You can always use 2NT by opener like after a 2♦ multi opening, but that makes strong hands a problem indeed. I prefer using transfers instead, at least opener already knows the suit.

An alternative might be to have only ♠s as the strong version, and do something else with strong ♥ hands. That way opener can usually bid 2♥ and responder can clarify his strong hand from 2NT up.

[dake50]

Doesn't this handcuff opener? He can't reasonably show his stuff
yet for fear of very weak. Can you design rebids after 2H eg.
to sort these out?
I've heard this 2D as very weak Major OR strong JS in a *minor*.
That at least often allows 3C,3D to start strong, even slammy auctions.

[awm]

Opener's strong hand would seem to be no problem -- just bid 2NT. If responder somehow has a strong jump shift opposite opener's strong hand you can probably just blast a grand or something; in any case you have a slam force and thus a huge amount of space.

The more interesting question is continuations after 1m-2♦-2♥. It may depend on exactly what sorts of hands you bid a strong jump with, but maybe something like:

2NT = really big balanced hand (not clear about major holding, but partner can bid 3om to ask)
3m = SJS with S+minor
3om = SJS with H+minor
3M = SJS with one-suiter

Over 1m-2♦-2♠:

2NT = really big balanced hand
3m = SJS with S+minor
3om = SJS with hearts; sets hearts as trumps and asks cuebids
3♠ = SJS with spades