There's no "best" answer. I tend to operate the way you do: Mainly in 4, use 5 for tests or fancy renders. I keep the two runtimes separate, and keep most things in the 4 zone, for two reasons: (1) Anything produced by 5 will give a "Later version than expected" warning message when run in 4. (2) P5 can read stuff from outside its own zone, but P4 can't. So it makes more sense to keep the bulk of stuff in the 4 zone.

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