Etch loss using 1 oz Cu in flex

Could anybody please tell me - what is the etch loss for 1oz cu (SMT only not mixed technology) in flex PCB. Can it be traced back to any IPC or mil (50884c) spec. Usually I take it as 1mil with 1.5 mil of plating on 1oz with ideal etch factor of 1. What if I don't plate but go for dev->etch->strip what would be the etch loss then? Please Help.

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