All Doubles by Responder are PEN
Doubles by Opener are extreme shape, desire to compete.

2H (X)
…… PASS then X is PEN
…… XX Co-operative Penalties, next X PEN
…… any M to play.

SYSTEM ON through a X, off through an overcall
…… 2NT = C or GF M
…… 3C = D or INV M
…… 3D: Pick A Major, possibly not GF through a X

If they intefere over our 2NT* or 3C* then opener must assume Responder is Weak long minor
2H* (P) 2NT* (3D) assume long C

A subsequent M bid would still be GF M
Double by Resp is still PEN.
A Cue Bid by Resp would be 'pick a Major'

If they interefere over our 3D resp, Opener can assume GF pick a Major,
PASS with Equal length, but try to show longer M otherwise.