Jax1I would think 3 CR123s should be fine, 3 RCR123s may not be. It's not only a question of overloading the LED, but also the control circuitry. The voltages on 3 CR123s work out to only a little more than the 2 RCR123s peak, so that should be safe. I would expect to blow something before you get to 5 or 6 batteries.
XenoMuseDepends on if the actual light and the battery have those safety features. Basically what olights have so you can't ruin a light if you accidentally put a battery with positive and negative on 1 end in a light that doesn't support that, and the overcharging safety cut off. I'll look into this and see if I can find something