Huibertus, on 2025-August-05, 04:22, said:
If you can be sure partner will always describe his hand accurately before making a quantitative invite with non 4333 hands without a 4 card major, so you know how to evaluate your own hand, then he is 4333 without a 4 card major and this is a pass.
If you aren't sure it is impossible to decide as he might well have a source of tricks like a 5 card minor that makes 6 cold, in which case pass and 6NT are equally bad gambles.
I have the ability to put the cube back to partner so I bid 5N to show a decent but not stellar 16 and let partner look at his shape and intermediates and decide (yes he can have 5m).
If you put a gun to my head and said 4 or 6, I'd bid 6.