[djehuti]

I'm looking for a follow up structure for this.. 2NT shows an unbalanced 4Major(responder's Major) 17+ OR 6+minor 17+ no 3card Major(responder's Major).
I'd like to be able to sign-off in the minor, and to GF relay knowing a) if it's the long minor it's shortness and b) if it's the strong fit hand, it's shape ( some kind of GAR structure), ideally distinguishing between 4M and 5+M from responder's relay's . Any ideias?
Thanks.

[Free]

I think you don't have much space. Idealy 3♣ should be a relay. But if opener's minor is ♣, then you can no longer signoff (unless in 4♣). After 1♣ openings you would need 3♦ as a relay, but this loses even more bidding space.

Knowing about opener's shortness is rather easy imo, usually it will be responder's Major since opener has 0-2M. But there are exceptions which you have to cover anyway (7321's for example). Perhaps it would be better to use 2NT for hands with long minor and 3M support, and your other bid (I guess 3m?) to deny the fit. In that case you only need to show 2 shortnesses or balanced (1m-1M-2NT-3♣-3♥/♠/NT) and use 3♦ and 4♣+ for various hand types with 4M support.

Also note that responder needs another option to show a 6 card M, just in case opener has a stiff honour or a doubleton M support. You might be looking for game only. I don't think there's room enough to show the difference between 4 and 5 card M by responder.

[djehuti]

Thanks Free.