gszes, on 2014-October-08, 13:48, said:
I would choose 3d for the reasons you mention above because I can then convert anything p bids to spades (even if it is 5s)
and they will know I have a slammish hand but need controls in the rounded suits. If p bids 3s hopefully we are playing
serious 3n so we can get a cue bidding sequence started.
This is not unreasonable. However, there is a reason to pick 3C. Opener can bid 3D by agreement as an acceptance of clubs. By doing so, Responder can then bid 3S as "I was just kidding about clubs."
3D doesn't work, because Opener needs 3H as natural with 5 in case Responder has, say, 5314 shape.
The 3S kidding bid would show a six-bagger, by the way, in this method. It is also used for long hearts.