Try 60%. That will give you 2.2FC in 9 hours of run-time. Might be a bit too much, but easier to lower output % than not add enough and get algae...
You may find, with that big of a pool and summer UV, that you will need to run your pump longer. It may be worth getting a 2-speed or VSP so you can run low RPM and make chlorine all day, and reduce your electrical expense.