I'm preparing a volume submitter document and trying to decide what the benefit is in submitting the plan for determination regarding the ratio percentage test. Can anyone help with this? Is there any advantage to completing question 11 on the 5307?

Since IRC Section 410(b) is an operational determination, I don't see any benefit in including that information in the FDL application. It's easy enough to figure on your own and the favorable letter cannot be relied on for 410(b) coverage in subsequent years, anyway.