First of all, hot adjustment specs are 0.25mm and 0.30mm not .025mm and .030mm! Secondly, your Z club fellow probably meant .011 inches not millimeters...
You need to get the units straight. Also make sure that you are using the correct set of feeler gauges, standard or metric. I'd pull off your valve cover and take a look at your valve train carefully at this point.
0.25mm and 0.30mm translates to about .010" and .012" FWIW.
*I got the specs from the 240Z FSM, assuming that valve lash between 240Z and 280Z is the same.