[Kungsgeten]

Currently in our Swedish Club system (where 1C is 12-14 NT, or most 17+ hands, or three-suited with short diamonds) we play transfers when they interfere at the one level. The exception is after they overcall 1S, where we play constructive negative free bids (GF vs the strong hand, about 7-11). A downside of this is that most GF hands have to start with a double, or jump to the three-level (or cue bid). Also transfers are pretty nice after they overcall, since it often puts overcaller on lead.

We've been thinking of using transfers, starting at 2C. We then give up stopping in 2C, but perhaps that is a small price to pay? If we have clubs we'll be forced to bid at the three-level, or perhaps put weakish club hands in the double (don't know what's best). So I'm looking for ideas

My current idea (7+ hcp is just a guideline, the real definition is probably "GF vs strong hand"):

1C-(1S)--
Dbl = Take-out with 7+ hcp. Could be less than INV with clubs.
1NT = Natural.
2C = 5+ diamonds, 7+ hcp.
2D = 5+ hearts, 7+ hcp.
2H = Non-forcing with 4H and longer minor, about 7-11 hcp.
2S = 5+ clubs, INV+. Forcing to 3C.
2NT = Natural INV.
3C = 5+ clubs and 4+ diamonds, 7-11 hcp.
3red = Preemptive.
3NT = 13-15 "to play".

The main issues is what's included in the double (which hands without 4 hearts, for instance), and the use of 2H, 2NT and 3X. I think 2S as clubs INV+ makes sense, put perhaps 3C as natural is better than both minors (then weakish with clubs could be excluded from the double). Balanced invitational could perhaps be included in the double, freeing 2NT for something artificial. I like the concept of being able to show some two-suiters, but I'm not sure of how much use it will have in practice.

[the hog]

Why not
1C/D (1H) x = 4S or 5 bad S 1S = t/f to 1Nt 1NT = t/f to 2C 2C = t/f to 2D 2D = GF with D 2H = t/f to S at least 5 good

[Kungsgeten]

That's similar to what we play, but that's over a heart overcall. I think a spade overcall makes it harder to play transfers.

[nullve]

My "NAT unBAL or 11-13/17-19/26+ BAL 1♣" / "NAT unBAL or 20-22 BAL 1♦" system can probably easily be modified into a playable Swedish Club system where

1♣-(P)-?

1M-1 = "0+, 4+ M"
...1M: includes 11-13 BAL w/ 2-3 M
......(...)
......2♣ = "GF, unBAL w/ 5+ M"
......2♦ = "Multiinvite or 16-18 BAL"
......(...)
...(...)
1♠ = "0-6, no major" OR "GF, either unBAL w/ primarily D or BAL and either no major or 4M333"
......1N = "non-forcing Gazzilli": either 11-13 BAL, "16-18 unBAL w/ primarily C" or 17-19 BAL
.........P = "0-6"
.........2♣ = "GF, unBAL w/ primarily D"
.........(...)
1N = "7-12, 3-S3-H5-C" (i.e. "NAT")
2♣ = "GF, unBAL w/ primarily C"
(...)

and, similarly,

1♣-(1♠)-?

P = "0+, 4+ H"
...X: includes 11-13 BAL w/ 2-3 H
......(...)
......2♣ = "GF, unBAL w/ primarily H"
......2♦ = "Multiinvite or 16-18 BAL"
......(...)
...(...)
X = "0-6, 3- H" OR "GF, either unBAL w/ primarily D or BAL and either no major, 4M333 or 4S4H"
...P: allowed
...1N = "non-forcing Gazzilli": either 11-13 BAL, "16-18 unBAL w/ primarily C" or 17-19 BAL
......P = "0-6"
......2♣ = "GF, unBAL w/ primarily D"
......(...)
1N = "7-12, 3-H5-C" (i.e. "NAT")
2♣ = "GF, unBAL w/ primarily C"
(...).

But this is probably very far from what you're looking for.

[shevek]

This is similar to what we do when our 16+ 1♣ is overcalled by 1M.
Here are some differences

1♣ -(1♠) - ?

2♥ = balanced-ish GF, no spade stopper
2N = natural GF
3♣+ = various naturalish GF

Better not to overload double.
2♥ = ♠xx ♥xxx ♦AQxx ♣Kxxx
so think "balanced GF with no stopper". Don't like to double with this.

2NT NON-forcing is awkward. Don't want to catch opener with a shapely hand.

[fromageGB]

Your 1♣ is not that different from mine, which is a 12-14 NT, 17-20 semi-balanced no 5 card major, or 12-20 3-suiter short in diamonds, or 6+clubs
Over a major overcall we like to distinguish between 4 and 5 cards in the other major, and show the strength range. Our normal methods uninterrupted are to have 1♠ as a relay, effectively being a transfer to NT (distinguishing the 3 opener ranges) or a minor, which rebids over the normally elicited 1NT to show whether the minor is weak, invitational, or GF. The transfer to NT can be raised if invitational or better, so the 2NT reply is freed.

The methods we adopt may translate to your opening.

After interference, it is even more important to right-side the NT, and we keep the same basic methods : over (1♥) 1♠ is still the relay, and over (1♠) X is the relay. As minors are shown after the relay, immediate minor bids are used to distinguish the length and strength of the majors.

After 1♣ (1♥) :
X = 4 spades weak
1♠ = relay
1NT = 5 spades weak
2♣ = 4 spades invitational or better
2♦ = 5+ spades invitational or better
2♥ = 6 spades weak
2NT = both minors
3m = preempt

The same after 1♣ (1♠) but you can no longer distinguish 4 or 5 weak hearts :
X = relay
1NT = 4 or 5 hearts weak
2♣ = 4 hearts invitational or better
2♦ = 5+ hearts invitational or better
2♥ = 6 hearts weak
2NT = both minors
3m = preempt
In both cases, a 2♠ bid can be used for a different hand, maybe 2-suited major-minor. We have not got into that yet.
Opener knowing both the length and strength of responder's major makes it very easy to take the correct action after a 4th seat opponent's bid such as a raise, ie support or perhaps X for penalty.

It works for us, and it's an idea for you.