i like the gap. gives it a little softness and lets you know when you've given it a real hit. good for resting your fingers on the pad for a push.
you could always rest your fingers on the pad for a push if you set your threshold higher
the gap makes it far more difficult to get repeatable low-level hits reliably since there's that crappy buffer zone in between pad and sensor.
someone in the 500 forums (completely isolated from me and my silicone advice) came up with the same trick. it is a night and day difference.
the "large" style pads of the 2500 are cast without this gap. same with the mpd series.
the 500 does have the gap.