You will use a variant of Rubensohl convention in response to your partner's 1 NT opening, but, after a Cappelletti overcall, there are some modifications. Here is the approach we propose.
After a Two suiter overcall (2
♦, 2
♥, 2
♠ or 2NT)
- any level 2 bid is natural
- Above 2 NT any bid is a Jacoby transfer. 2 NT is artificial (Jacoby for ♣)
- An impossible transfer becomes a Stayman
- A double is a take-out double : it could be a Stayman with 8 HCP, or show a balanced hand with 8 HCP or more.
After a double
- bid as if there had not been an overcall
After a 2♣ overcall (one suiter)
- bid as if there had not been an overcall and use Double for Stayman