Art Dept Budget for Sci-Fi/Period Indie - Overcoming the 10-20% Rule?

Hey everyone, as a Location Manager, I'm constantly wrestling with budgets, and I've got a genuine head-scratcher. We all know the general guideline of allocating 10-20% of your total budget to art department. It’s a solid starting point for many projects. But what happens when you’re doing something visually demanding, like indie sci-fi or a period drama, on a shoestring? The art department is inherently going to need more resources for props, set dressing, and sometimes even builds, just to establish the world. I've tried to get creative with sourcing, repurposing, and heavy negotiation with vendors, but it still feels like we’re fighting an uphill battle to keep that percentage in check without compromising the look. For those of you who've tackled these genres on an indie budget, how do you adapt that 10-20% art department rule? Do you just accept a higher percentage for art, or are there clever strategies I'm missing to still hit the visual marks without breaking the bank?