How to make this ray traced GI less grainy

Hello. I am working on a warehouse interior for a work project, and I am trying to use ray tracing in this scene. However, near the ceiling where all of these support beams are is really grainy at the moment. It is most likely because those areas are not directly lit, but is there a way to improve the look without sticking a bunch of lights up there? My ray traced GI settings in my post process volume are Final Gather Type with Max bounces at 1, and samples per pixel at 16. If anyone can help out with this I’d really appreciate it, thanks!