At my US company, flap 3 is “encouraged” but most people go with full. It’s at the discretion of the PF. My preference in your situation would be full. We do a few approaches to places where the glide slope is a bit steeper (maybe 3.3, I think), and flap 3 still works fine. I think the major hurdle would be getting stabilised earlier.
That said, 8kg of fuel is less than a rounding error on the gauges. The fuel bowser typically delivers a bit more than the number that’s dialled in. On my last flight, we were over fuelled by about 25 times the 8kg we’re thought to save with flaps 3.