[straube]

1C-1D strong, weak or GF
1S-2S 4+ spades, weak with exactly 3 spades

If opener has 5 spades, it's easy. If opener has 4S/5m I have a problem.
For continuations looking at

2N-5+C, forcing
.....3C-no fit, 0-2
..........3D-4-1-3-5, f
..........3H-4-3-1-5, f
..........3S-?
..........3N-?
.....3D-no fit, 3-4
.....3H-fit, 0-2
.....3S-fit, 3-4
3C-5+D, forcing
.....same steps
3D-4-1-5-3, f
3H-5+S, inv
3S-5+S, f

I'd like something better and simpler.

[straube]

Maybe drop the fit/no fit responses

2N-GI, 5+C
.....3C-club preference, weak
.....3D-5D, f
.....3H-5H, f
.....3S-short C, weak
.....3N-other (2+C then)

3C-GI, 5+D
.....3D-diamond preference, weak
.....3H-5H, f
.....3S-short D, weak
.....3N-other

3D-5S, game try

3H-4-1-5-3

[shevek]

Why do you say
"If opener has 5 spades, it's easy."?

It's not. Opener needs some sort of trial bid here.
We play

1♣ - 1♦
1♠ - 2♠

2NT = start of a short suit trial, usually 5 ♠s
3m = natural, not forcing
3♥ = long suit trial, balanced-ish
3♠ = invite, usually 6♠s

Note that we play opener's 1♠ as limited, 16-19.
Stronger hands rebid 1♥ as 19+ any

[straube]

shevek, on 2019-September-27, 21:00, said:

Why do you say
"If opener has 5 spades, it's easy."?

It's not. Opener needs some sort of trial bid here.
We play

1♣ - 1♦
1♠ - 2♠

2NT = start of a short suit trial, usually 5 ♠s
3m = natural, not forcing
3♥ = long suit trial, balanced-ish
3♠ = invite, usually 6♠s

Note that we play opener's 1♠ as limited, 16-19.
Stronger hands rebid 1♥ as 19+ any

Unlike your method, our 1S is unlimited, so we have a problem holding something like 23+ 4-1-3-5. We have to look consider that we might belong elsewhere than spades and we have to be able to both invite and force game opposite a hand that is 0-4 hcp and not 0-7 hcps.

It would have been more precise to say that when opener holds five spades, it's "comparatively" easy because reaching a fit at the point of 2S is much easier than restarting to find one.