I regard Multi vs Multi as a specialized version of Unusual vs Unusual. X
remains “penalizing” either suit but longer. Cuebids are reordered and show
unbid (minor) suits.
Here I recommend a modified version of Rumpelsohl.
Frequently pass 2♦x with 4+ diamonds to ease slam exploration, especially for
minor suit slams.
(2♦) X-
OPT: either major or 19+
2M!
P/C
2NT!
INV+, REV LEB
3♣
PRE, usually 5+♣
3♦!
INV+ TRF, 5+♥
3♥!
INV+ TRF, 5+♠
3♠!
FG TRF, usually 6+♣
3NT
To play
4♣!
STR choice of games
4♦!
PRE choice of games
(2♦) X-2NT
REV LEB
3♣!
P/C, 12–14
3♦!
S/T, 18+
3M
NAT, 15–17, 5+#
When RHO bids, X is penalty and usually short in the other major. We play
Rubinsohl here because we need to bid diamonds. Please refrain from penalizing
with length in both major suits. It is usually better to make our own contract
than setting their doubled partscore.
(2♦) X (2M)
P/C
X
PEN, good 4+# and usually short in the other major
2♠!
P/C
2NT!
TRF, 5+♣
3♣!
TRF, 5+♦
3♦!
TRF, 5+OM
3♥!
P/C, INV in ♥, INV+ in ♠
3♠!
P/C, INV in ♠, FG in ♥
(2♦) X (3M)
P/C
X
PEN, usuaully short in the other major
After opener shows their major, doubler always penalizes when holding the same
suit. This action is mostly safe because doubler sits behind the opener. More
importantly, this treatment creates a negative inference that a pass implies
holding the other major.