Lone Eagle.
I would imagine an Irvin would be perfectly acceptable, but should only be worn when within visual range of the aircraft.
I have flown in a Tiggy and would recommend leather for windproofing and a scarf to seal the gaps around the neck. Silk is NOT required. That was used by fighter pilots who used to swivel their heads about looking for possible attackers and got their necks rubbed raw on the rough serge from which their uniform was Made.
Regards
Mike W