I tried to use a regular 17mm key and I just couldn't get those nuts off... I had run out of pb blaster so I'm going to try again this weekend...
I didn't even trim the "front" plastic part I just detached the two pieces put the front one back on and "sandwiched" it underneath the metal skid plate.. I assume it was a little trickier to do it my way but I didn't need to trim anything... and I believe it eliminated the vibrations...
RULE #1 You got to pay to play!
RULE#2 If you can't Live by rule 1... Don't Mod your car.