helene_t, on 2018-February-22, 20:12, said:
I am just worried that the parity is not always enough to clarify the number of keycards held. But maybe Fantunes had a way to resolve the ambiguity
That's the least of problems when you actually play Turbo, believe me.
Much like "only" knowing that the number of Keycards is 1/4 or 0/3 after a RKCB
The real problems in my experience are:
(1) you give up other uses of 4NT and 5NT within the control-bid sequence, such as showing a further control in the last suit bid, or a simple waiting relay to "rightside" the bidding
(2) sometimes it will be the "wrong" partner who gets the opportunity to bid Turbo as his partner is not in a good position to judge the contract (but not that often)
(3) sometimes the need to bid Turbo will "wrongside" the bid about Clubs (but equally often it will "rightside" things).