My concern is also trying to stay near the peak of the efficiency curve, which may be at 70 - 80% of max power. An oversized power supply running at 50% capacity may be less efficient, which may matter for heat dissipation or a battery system.
Would've aced it but I put 50% in Q2. I'd still stick to that, unless it's a very high and known steady load. For small power supplies, whether linear or switching, running them close to max load is asking for trouble, usually early failure, and the extra investment in a bit more capacity will repay itself in reliability,