Paul, if im totally honest with you its fae easier to get the body shop to do this for you with a plasma cutter.

I have trimmed my arches up to 5mm below the holes where the arches bolt on.

You have all the room in the world then...

the only other areas that casue issues are where the lip of the arch is behind the corner of the font bumper the wing bends inward there so this needs trimmimg too.

as on the rear where the rear bumper joins the arch kit, this flares into so needs trimming.

I have no arch rubbing whatsover on 16" wheels, although i now run 15".

For the body shop to cut it they will charge you a minnsicule amount compared to you spending a weekend with an angle grinder and a run up..

The plasma cut looks so clean and factory like....
then just tiger bond the kit on after.