I always consider the forces on the airplane ..... https://www.avweb.com/flight-safety/technique/turbulence-v-speeds/ Do the sums on gust loads.
Manoeuvring loads and structural fatigue are adversely affected by overweight operation. So is performance but, as you say, a big engine is good. 20 kg .... 3% maybe .... almost trivial compared to those aeroplanes found to have incorrect empty weights a while back along with a gross error in crew moment arms so their CG was way further aft. Fixed by adding mass on the engine - a much bigger % increase - what effect does that have on the engine mount and forward fuselage structure?