It doesn't weaken it as there is a full metal backing on the actual pedal, the plastic cover is quite strong.
All you have to do is cut enough of it away so that the cover sits around the actual pedal.
Here's the pedal and the plate you have to clear;
Here is the back of mine, not pretty but you can't see it from the front.
Here it is installed
The pedal is still strong, it doesn't move or slip at all and has made all the difference for me anyway. Just have a stab at it, the worst that can happen is you put the old one back on.