I'm gonna go with "don't be stupid" again. Putting stuff down on your floorboards that interfere with the full operation of the controls is asking for trouble. Your device could fall into the brake pedal, preventing operation. It could catch your foot at a critical moment. It could just surprise you after a long period of inattentiveness by acting "different" than what you're used to.

You want it to be a 'safe' device that simply prevents over acceleration. It comes with a royal boatload of possible unintended and unimagined consequences.

Don't be stupid.

Edit: (On reread). If "don't be stupid" makes you feel angry or defiant, please read it as "Please don't do this. Its more dangerous than you think.", with my apologies for sounding parental.