New convention: The 6NT Try

You and partner have reached a point in the bidding where you determine there is a slam.
There are two reasons for this convention:
1. You are playing imps and you are missing the trump jack, while you have a bit extra on the side and, therefore, 6NT might be a safer contract.
2. You are playing matchpoints and since 6NT scores more than six of a suit, you are interested in reaching 6NT if 12 tricks are there without the need of a ruff.
The 6NT Try is the "suit below the trump suit at the six level."

Example:

opener	responder
A x x x A J K Q J x Q 10 x	K 10 x x K 10 x x A x A K x
1NT	2
2	3 (*)
3	4 NT
5	6
6 NT	-

*-slam try in spades

After a 15-17 notrump, responder uses Stayman, locates the spade fit, and checks for aces. Assume that Responder's 4NT is Keycard Blackwood. Over 5, he knows that the queen of spades is missing. He also knows the partnership has at least 32 HCP. So he bids 6 "6NT Try" and opener, with extra values, chooses to play in 6NT.

Suppose opener held:

A J x x
A x
K Q x x
Q 10 x