First off, don't cut the lip. If you do a search for the" $5 lip" you will see many post. I wrote and I remember several doing write ups on how to install the lip. You will need a heat gun, keep it moving and on low, so you don't get it too hot. I bought a package of 3/8ths -1/2" SS large pancake head self tapping screws and a roll of 3/4" wide 3M double face tape. This is used to attach trim parts on cars. I used 3 peices of the tape about1 ft long each and installed along the inside top edge. I started about 4 inches from each end, and also put a piece on each side of the center of the lip. I wrapped the lip from one end and put screws in the part that looks like a mounting flange using the SS screws. I slowly wrapped the lip around the bumper and pulled the red facing off the 3M tape being careful to keep the lip lined up with the line on the bumper. When I made it completely around I added SS screws along the bumper bottom( one every 6-8 inches).
Find the post for the $5 lip, you should find many pics of the install.Everyone did something slightly different, but the installes are all similar.
there are many POST on this I think mine start at #160, but keep scrolling down as there are many. I did make one cut to the lip, a "V" notch in the center bottom about 3/8 to1/2" wide, it tapers from back to front most narrow.