hydraulic to mechanical rocker assy. swap?

[drof 89]

When you change from hyd. to mech. rocker arm shaft assemblys is there a safe cold gap setting that can be used? The Haynes only gives a hot or warm setting. I just don't like the idea of bolting on a cold or cooler unadjusted rocker shaft assembly on a hot engine. Does anyone know if the warm set gap of 0.012 opens wider when cold or closes tighter when cold? I'm sure the factory did it all cold. But what setting did they use? Thanks