Not to unnecessarily complicate the subject

, but WHEN does a spey outfit need to be in balance? During the cast, which takes just a few seconds and during which the dynamics of balance are in radical flux? Or during the cast's downstream drift, when current drag against the line reduces the reel's counterweight effect, and which goes on for much longer than the cast?
My greenheart beast is downright hard to hold horizontal during the drift period, even though it's fitted with a honkin' heavy mooching reel.
For most rod/reel combinations, balance doesn't seem to be a critical problem. Let me propose this simple standard: If the balance point of a rod and reel, with all line in the reel, is within two or three inches of the top of the handle, balance is good enough.