[kgr]

You are bidding a 1st/2nd control and opps DBL.
Example:
1S-(p)-2H-(p)
2S-(p)-3S-(p)
3NT-(p)-4C-(DBL)

...-4C-(DBL)-?
- RDBL= 1st control C
- Pass= Waiting to see if partner can RDBL
- 4S= no control C, minimal hand; only if contract will have to be played in this hand.
- 4D/H= 3rd control C (CQ or xx), not interested in 1st control C for 7. Trying for 6.

...-4C-(DBL)-p-(p)-?
- RDBL= 1st control C
- 4D/H= only 2nd control C
- 4S= 2nd control C, no control in between suits OR just minimal for previous bidding

Are these agreements best or can we do better? (The example added for clarity. Maybe you would never bid 4S as opener in this example, but I'm most interested in the generic agreements).