zSFP power supply requirements

[UStralian]

I'm designing a board with a couple of zSFP connectors on it. I don't know what modules the end user will be plugging in to it, but I want to support as broad a range of performance as I can, within reason. They'll only be fiber, not copper modules. I need to decide how much power to give the ports. I can't find any good design guidelines for zSFP in general, only loose anecdotal evidence. I'm using a reference design that feeds them from a fat rail with 5A inductors, and I've spoken to another engineer who has used QSFP modules that pull 2A. All I can find are modules that pull <300mA, and the connectors themselves appear to be rated up to 500mA/pin. Is there a good reference somewhere for how to design SFP interfaces without way overdoing the power supply? Or at least explain the discrepancies I'm seeing in power budgets?