I've found Wesley May's recent post http://bridgewinners.com/article/view/alerting-when-theres-no-agreement/ and here's a similar question, this time with a poll attached.
NS were playing MOSSO http://bridgewinners.com/article/view/introduction-to-mosso-mosca-with-standard-spade-openings/ and the 1♣ opening showed either 13+ with clubs, 17+ with 5+ spades or a balanced hand with 12-14, 18-20 or 23+ points. (The system fully meets the criteria associated with this event.)
In the EW system the 2♣ overcall would show the red suits over a natural (or short) club. Over a strong (e.g. precision) club it would show the minor suits. They had not discussed the meaning of 2♣ over a Polish-style 1♣ opening.
2♠ showed about 17-21 with 5+ spades.
Neither East nor West alerted or gave any indication relating to the bidding until the hand was over. 5♥ doubled made exactly and NS scored 0%.
South claimed that he would not have doubled 5♥ if he had realized that 2♣ showed the red suits. A pass over 4♠ would have been forcing.
North's approach was to trust his partner, despite knowing of a 12 card spade fit.
When the hand was over NS called the director, claiming that they had been damaged by misinformation.
EW maintained that they had no need to alert or explain anything as they had no agreement.
The director (after consulting with 2 or 3 other people) ruled that the result should stand.
NS appealed (paying a £20 deposit), mainly on the basis that East should have bid 5♣ rather than 5♥ if he wasn't going to alert at any stage.
If you were on the appeals committee, how would you rule? Please choose one of the options below. The middle one means that the result stands some percentage of the time and is otherwise adjusted.
Also, any further comments on alerting when there's no agreement would be welcomed.
Plus... it's free!