So...if the engine is currently running. Set the lash hot as specified, then record the lash after it cools down to room temp. There is your cold spec.
Typically you can go .002 from the factory lash spec without issue. Sometimes you can go .004, even .008. You can definitely do that with a purple shaft cam. 28/32...used to run 24/28. Even ran 24/24.
Remember, while a little valve train clatter may be annoying and you may lose a few HP, a loose valve is much happier than a tight valve.
Respectfully, it's the other way around. It's better to have a more gentle ramp than to hit it at a steeper than designed point. I'll always start tight and at the most I'll go .002 looser. But again as has been mentioned, it's a tuning technique.