The majority of the field ended up 6♦ or 6NT, all making, causing me a big loss of -7.1 IMP.
Those who bid slam generally went, for example:
1♥ - 6NT
1♥ - 2♣
2♦ - 6♦
1♦ - 2♣
2♦ - 2♠
2NT - 6NT
or bidding 6♦ / 6NT after the use of RKCB showing that 1 keycard is missing, such as
1♥ - 2♣
2♦ - 3♦
4♦ - 4NT
5♦ - 6♦ / 6NT
or
1♥ - 4NT
5♠ - 6NT
Opposite a minimum opener, there may not be 33 HCPs required for a balanced 6NT. How do people know a slam will make, when there were not enough points available and RKCB showed 1 keycard missing?