[DinDIP]

Is the Kaplan inversion permitted under the ACBL midchart?

Does your answer depend upon opener's rebids (i.e. a 1N rebid that shows a BAL hand is OK but a 1N rebid that shows 4+S is not)?

Would your answer be different if 1S could be EITHER a normal forcing notrump (minus hands that would bid a NAT but NF 2/1) OR any GF?

Background: My partner and I are planning on visiting the USA to play in the Vanderbilt and other events in New Orleans. Here in Australia we play a Moscito-like system. Parts of that are not permitted under the midchart so we're making some non-trivial adjustments. One thing we'd like to do is use 1♠ as a Kaplan Inversion after our 1♥ opening, showing either a BALish 6-11 or any GF. (This is because our 2/1s are NAT NF.) Our intention is to open 1N or 1D with all BAL hands including 5M332 so 1M promises an UNBAL hand. After
1♥-1♠
we propose to play essentially NAT rebids, but with 1N = 4+S. A new suit by responder would be NAT and GF, although we could use step as a GF relay over 1N (and 2C) as that's permitted under GC#8.

However, before doing all the work involved and the practice so we're comfortable with these new methods we'd like reassurance that they are legal. A member of the ACBL Convention and Defense Approval Committee offered me the personal opinion that the second-round continuations were OK but noted that the 1♠ response might be considered to be the start of a non-GF relay system, which is prohibited.

David

[jeffford76]

 DinDIP, on 2014-December-08, 20:44, said:

Is the Kaplan inversion permitted under the ACBL midchart?

Yes, it is allowed. Basically all constructive response are allowed with an exception for non-game-forcing relay systems. Kaplan Inversion is not a relay system.

[mgoetze]

 jeffford76, on 2014-December-09, 01:45, said:

Yes, it is allowed. Basically all constructive response are allowed with an exception for non-game-forcing relay systems. Kaplan Inversion is not a relay system.

But you did notice that OP is not asking about Kaplan Inversion, but rather a similar convention he's giving the same name to in order to confuse people, right?

[DinDIP]

 mgoetze, on 2014-December-09, 03:55, said:

But you did notice that OP is not asking about Kaplan Inversion, but rather a similar convention he's giving the same name to in order to confuse people, right?

Our intention is not to confuse or mislead people. We want to be able to do over 1♥ what we are able to do with a forcing notrump. (In response to 1♠, 1N will show a BALish hand of 6-11 HCP, a three-card limit raise of spades, or any GF. My reading of the GCC is that this is permitted: the prohibition is that 1N cannot promise game INV or better values.) We could use 1N in response to 1♥ to show the same set of hands (all perfectly legal) but now a NAT 2♠ rebid takes us past our 2♥ safety threshold when responder is weak. It's the same reasoning that led Kaplan (and Richard Granville in the UK and others elsewhere) to switch the meanings of the 1♠ and 1N responses.

My question is: If it is legal for a 1♠-response to 1♥ to show forcing notrump-type hands, does that extend to forcing notrumps that include strong hands?

David

[mycroft]

The relevant part of the Mid-Chart is (ALLOWED, with a pre-Alert *and a written description* but without requiring a defence):

3 All other constructive rebids and responses are permitted - except for:
a. relay systems that show less than game-forcing values

So, unless 1♠ "is the first relay", even when it's GF (because the initial 1♠ call does *not* guarantee GF, even if it does when the relays start), you're good. I don't think you can use the GCC#8 regulation for

1♥-1♠;
some response-relay "oh, this one is GF, now we are in a relay auction" - because that makes 1♠ the first "forcing, tell me more" call. But this would be a difficult reading of the regs, and I'd want to check with Horn Lake (either way!)

Your 1NT response is also Mid-Chart legal, even if it were not to be GCC legal (which I agree it is), under the same regulation.

[JanM]

Just in case you don't know, and since no one else has mentioned it, the Vanderbilt is a Super Chart event, in which you can play Moscito or anything else you want (with some exceptions that I'm sure wouldn't apply to you). The Midchart is relevant for other events at the NABC.