I have been fascinated by the mesh of complimentary patterns. So, I have decided to think out loud about them.
Consider 5-4-3-1 pattern.
If partner has 4-3-3-3, We have a nine-fit. We are missing, in the high-honors, AKQ-AKQ-AKQ-A, for a total of 31 HCP's. Drop one high honor and we are in slam territory. That yields 27-29 HCP's. We need nine covers for slam, meaning three tricks from shape. The stiff and a three-card suit means that A-AKQ works as well as AKQ-A, or AK-AK.
Switch to 3433, though. We have two eight-fits. We are missing, in the high honors, the same AKQ-AKQ-AKQ-A, for the same 31 HCP's. The same stiff analysis works. If we play in the 5-3 fit, the same basic trick expectancy is there, albeit a bid shakier in trumps.
However, if we play in the 4-4 fit, the fourth and fifth cards in the long suit might replace the King and Queen of the three-card suit. With as little as AKQ-AKQ-A, we get to 11 tricks, and a bad lead gets us to 12.
The conclusion, then, is the 5-4-3-1 opposite 4-3-3-3 is much weaker than 5-4-3-1 opposite 3-4-3-3.
This is the pattern the leads to theory like the Empathetic Splinter, Serious 3NT by the hand making a simple raise (serious for the natural second-suit GT), and the like.
So, are there other pattern meshes?
One obvious is any set of opposing 5-3's. Consider 5332 opposite 3532. AKQ-AKQ-A-A makes 12 tricks. That's quite a nice combo, but it is still 26 HCP's. If you note above, the 5431-4333 combo was stronger. Of course, a stiff always helps, but I still find this interesting.
Some folks get excite by 4441's. How about them? Well, toss it against a nice 3253. AKQ-AK-AKQ-A, minus one, makes slam. Still not quite as strong as the 5431 holding.
This 5431 is quite a beast.
Let's try 5431 against other holdings. 4432? AKQ-AKQ-A-A? The extra card across from the 5-card suit gains little. If anything, it persuades us away from the more powerful (as to potential) 4-4 fit. Might have dummy reversal value but for the inability to take two ruffs. Switch 4432 to 4423, and we are getting somewhere.
Take from this what you will. But, I've sat and thought about this sort of thing for a long enough period of time to be taken away for my own protection and/or to conclude that 5431 is a pattern that has very unusually strong trick-taking ability, one that should receive more attention. It seems to produce magic tricks.
To see the magic, create a 5-4-3-1 opposite 3-4-4-4 that makes slam. Then, count the hand out by LTC. I'll bet LTC is off more than on.
Another beauty of the 5-4-3-1 is that is offers the dual possibility of the 5-3 + 4-4 OR 5-3 + 3-5.
Do you pay 5-4-3-1 its propers in your thinking and system?