Outer Limits 4x4 Board

Just did my tappets and set them at 15 thou.

Is there another safe setting I can set them at which is a little bit tighter.

My engine runs on LPG 99% of the time. Day to day running, no heavy stuff.

Also the manual states to do them whilst the engine is hot.

My friend allways does them when they are cold. If the latter then that would give a tighter overall setting when engine has reached operating temperature. Any problems long term with this