Yep, I agree. Four holes in each corner widened using a step drill to the size that I want (about 12mm). 2" duct tape (not masking tape) along all four sides to the outer edge of the step holes giving me the cut line. Then just cut along four straight lines and the centre piece drops away.
The trick for me though comes before this. I always have a panel template engraving manufactured. They are not expensive typically only £40.00 UK price. I use Pantograph Services (http://www.pantograph.co.uk/). They work from a dimensioned PDF (see attached example). As an extra this gives you text engraving around your buttons and indicators. it is well worth doing.
With the panel engraving as a template you mark out the position of the cutout easily getting perfect HMI line up with your buttons and indicators. Drill your four holes, widen them, add the duct tape, get cutting. A Bosche hacksaw blade in a mains powered jig saw works for me.
I pull the 22.5mm holes through with a circular hole puller, driven with a 1/2" impact driver. Works well up to and including 1.0 x 0.8m door panel sizes.
Not sure if it would handle stainless though. Never tried.