[Phil]

If 1C is usually a weak NT, has anyone use 1N as a GF relay? Is it part of any recognized structure?

[Kungsgeten]

I think many of the Swedish pairs use that treatment. I'm not sure if they use full relays or not. If 1C is natural or balanced I guess a simple solution would be something like:

1C--1NT;
2C = Minimum unbal
2D = Balanced
2H = 4 diamonds or three-suited, extras
2S = 4 hearts, extras
2NT = 6+ clubs, extras (you're quite high here though)
3C+ = 4 spades, extras

Or if you use 1M-2C as a GF relay over 1M, why not make it the same?

1C--1NT;
2C = Balanced or three-suited, not 5C.
2D+ = 5+C. As 1M--2C;

[helene_t]

Han plays this in his F2F partnership. Or at least he did last time I saw him.

Opener's rebids involve transfers, they want the described hand to be dummy obviously.

[Valardent]

I've been using it for years.

The way I constructed it; opener's hands are divided in 3 ranges, 11-13(min) - 14-16 - 17-22(max)

Opener's rebids are :

2C : all 14-16 (+balanced 12-14 ctrl max hand)
2D : min/max with 4+D or min 6+C
2H : min/max with 4+S
2S : min/max with 4+H
2NT : balanced 12-14 NT
3C : max 6+C