Speed alert - can you alter the overage amount?

Does anyone know if there is a trick way to alter the amount by which you must exceed the speed limit to trigger the alert? I was on Interstate 5 yesterday and found that the new 8.x maps have limits for that freeway. It seemed that the alert sounded at about 64 MPH in a 60 MPH zone. I would love to be able to increase that margin just a bit. The alert is a good idea, but could get REALLY annoying.

You can set a preference-->Safety-->Warn when going above a specific speed and then manually set it for the speed you want (like 68 mph).

Right, but you would not be very happy with that when the limit changed from 60 to 70 as it does on I5 in Washington. It would be great if you could set the exceed limit alert to occur when you were some percentage above the limit, whatever it was on the road you were on.

There's another thread open with this same question. The answer is that the 5 MPH over the speed limit is hard coded into the OS and cannot be changed. It's either on or off.

Thanks. I searched first, but apparently did not use the right search terms.

I think this is the thread 'sageuvagony' was referring to:

Over Speed Limit warning set point change? (ONE 3rd edition)