Unfortunately for Stone, that's not for the witness to decide. And Stone is an absolute 'effing moron for doing anything with that witness that might remotely be construed as "witness tampering."
Personally, I think Stone should get a medal for lying to Congress. But he should probably rot in prison for even agreeing to testify to Congress in the first place. They never sent him a subpoena. It was all just a staged PR stunt to him.
It seems to me that the biggest problem facing these Trump supporters who have been run through the wringer in the criminal justice system is that they have an average IQ of about 90.
I never knew Stone had not been subpoenaed to appear before Congress! Do you have a reference to that? If so, why in the &*#% would he ever appear before them?
I know, Stone thinks he's the smartest man in the room.