Hopefully this isn't something that has been beat to death on other postings. I am putting together a tactical build with a Defiance action that is coming with a 20 MOA rail. I want to order rings for a NF 50mm objective scope but don't know how low I dare order without running into mounting problems. Anyone have experience with this that can save me the frustration of having to try several heights before I find the right ones? BTW This is going on a Manners T2A with a heavy target barrel.