well i have that same lip and i was thinking the same thing as you. that it would hold up to high speed. however this is what i ended up doing. i just drilled holes and mounted it and hope for the best. then i just started pushing down on it a little. and noticed a little bit of movement. so what i done is got some J B weld to help seal it to the body a little bit better. and it's hold pretty good like this. you cant see the JB weld or anything on my car. and just this weekend(yesterday matter of fact) i took it up to 150 numerous times with out any problems at all. hopes this helps but i was concerned with the same thing when my lip first came in.