[Oksamit78]

Well... if you are leaning towards use of velcro, aka hook-n-loop, you should consider using the so-called snap-together fasteners together with screws. The principle is similar to velcro, but instead they use mushroom shaped plastic stems and heads to interlock with each other. These are used in automotive a lot to hold bug deflectors and such to be easily removed at car wash.

Here is an example by 3M: https://www.3m.com/3M/en_US/p/d/b40068902/
Follow 3M recommendations as to how to establish the strongest engagement by selecting the combination of stems' density (250:400 is the strongest).

You should use the strips with acrylic adhesive (not rubber) as it is the best choice for exterior use.

Unfortunately, the only problem with using strips like that is the resultant gap that they will cause between the lip and the bumper cover - approx 3.86 mm (when strips are mated into each other), which is a lot and not cosmetically appealing without filling the gap up with custom silicon seal. I've made such seals in the past using a caulking gun and having mold release applied to one of the two surfaces (bumper cover). As the result - the seal gets permanently attached to the lip and is removed together with the lip whenever you take the lip off.

Good luck.