Playing on the last day of the Orlando NABC in the AX Swiss Teams, you pick up the following nice hand with everyone Vul AQ975 A42 AK AQ7. You are getting ready to decide how to bid this when partners open 2D (Weak) in 2nd chair in front of you, the opponents both passing. This now presents the problem in a totally different light. Systemically, there are 3 primary things you can do here, bid 2N (OGUST) to ask partner what kind of pre-empt this was, although you have some idea looking at the AK of Diamonds, or you can bid 3C, asking if partner has a high card feature in their hand. The last option you have, is to bid 2S to check if partner has any Spades support, this is forcing for 1 round.
You decide on option 3 and bid 2S over 2D, and partner surprises you by bidding 4H. You are not a regular partnership, and have not discussed this, but that certainly looks like Heart shortness with Spade Support, which is about as good news as it is possible to get on this hand. You bid 4N now, RKC in Spades, and partner shows in with 5C (1/4). This is certainly starting to look serious, the only question now is, how good are partners Diamonds?
Working under the assumption that partner should not open a very bad Diamond suit in 2nd seat, the non-weak pre-empt seat, and certainly should not bid 4H with something like Kxx x Jxxxxx xxx, I think you should gamble out 7D here. You can not count 13 tricks if partner has bad Diamonds or Spades go 4-1, but even with Spades bad, there is an extra chance, partner can ruff out the Spades and take the Club hook, if needed, for trick 13. All in all, I think your odds for 13 tricks come in somewhere in the high 80’s, certainly not absolute, but pretty solidly in your favour.
At the table, this hand bid only 6D, making 7 when partner held Kxx x QJT98x xxx and even though Diamonds were 4-1, Spades being 3-2 meant an easy claim early on the hand. At the other table, this hand passed, and now there was no practical way to find out about the massive Diamond fit and count 13 tricks after a 2C opener, Spade bid and raise. So a possible big pickup went out the window. Who says that weak 2D bids have no value.