Flap would be easier.
Steel bracket would be my preference, and by slow, careful work it could be done "Situ" (in place), but risk of damage to fuselage skin might be considered.
If you do the steel bracket, remove a few rivets, try and jam a stainless steel shim in there and start cutting by hand with hacksaw blade. Power tools like a Dremel might be a tad risky. Also you could just bevel or chamfer the edge of the steel bracket so it clears.