Running more exhaust filters would help alot. There's not much surface area in your pic which allows the clear to get through. Typical booth will have a lot more surface area. something along the lines of 12 - 20x25 exhaust filters.
Keep in mind even if you are 100% efficient in trapping the paint solids you are still gonna notice a solvent smell coming out of the exhaust.
Add on paint booth exhaust setups have a large plenum box between the fan & a wall of filters. Not sure what all you got there between filters & where the fan actually is, but removing your sampling board area & having filters to the outside of it would be a good start.