[Tom Goldman]

As the ad's say ,"your results may vary". ..I very cautiously use a hole saw at a medium speed that is one size smaller than the desired hole , and then hand finish with a fine half round file to the finished size.
It helps to use an extra long pilot drill to keep the saw from walking due to the padding thickness
I have tried the diamond abrasive hole saws ,they do work ,but require a higher speed and will usually cause the dash covering to try and melt to the saw , so you must keep the saw moving to prevent sticking.