Dereelight Xsearcher safest battery configuration?

New to the forum and looking for a bit of battery advise. I am new to running li-ion batteries in series and have read up on them and think I understand the limitations of CR123a vs protected 18650 cells. I have purchased a Dereelight Xsearcher which can run on one 18650 unregulated, two CR123a, two 18650, or 4 CR123a battery configurations. Per the manufacturer, the light has no low voltage protection and drops out of regulation at 5v which I believe means it will begin to dim at voltages below 5v. So once you notice the light dimming, I would think

two 18650’s would be at 2.5 volts each, and have tripped the protection circuits or ruined the batteries.

four CR123a would be at 1.25 volts each which is drasticly low and potentionally dangerous.

two CR123a would be at 2.5 volts each which is I think is about right for an exhausted CR123a.

Would you agree that two CR123a is the safest way to load this light or is there something I don’t understand? Your insight would be appreciated.

Two 18650 you will have no problems with. Back when I was leery of batteries I ran two 18350 IMR in mine.

the safest setup would be 2x 18650 or 2x 16430 protected, in series

thats what i ran in my dbs

OK then help me understand. The protection circuit in the battery is going to trip about 2.8 volts, (which isn’t good for the battery), but the light won’t even start to dim till the batteries get below 2.5 volts each, or 5 volts total. So what did you do, run the light till the protection circuits in the batteries tripped or just guess as how long to run the light before recharging?

If the protection circuit trips at 2.8 volts, then the batteries will stop discharging and the light will turn off when one of them gets to 2.8 volts.

It should dim before voltage gets that low.