I understand that a negative double after 1D - (2C) shows one major.
In one of his Mr Bridge articles Bernard Magee says that 8+HCP are needed for a 2 level negative double (he gives 1H - (2D) as an example, where responder is specifically showing spades. But with 1D - (2C) you might be holding either major, and partner might choose the wrong one. Should the required point count be higher, or should your hand be such that you can then bid 2NT, i.e. reasonably balanced with a good stop in the overcall suit, or both? I have trawled through lots of references on the negative double and have not yet found any treatment of this sequence.
And if the partnership is not quite ready for playing the negative double, what is the minimum requirement in suit length and HCP to respond with 2 of a major after this sequence?