SANYO dual 18650 with eGO Twist circuit *safety*

[freestylekc]

Hey all, this is my first post ... so bear with me.
I have a mod with 2 SANYO 18650 batteries (serially linked) and the circuitry from a dismantled eGo Twist 650mAh VV battery.
It works great, but I have a few safety concerns:

I know the ego twist circuit has protection to short-circuit and discharge, but is that still useful in the new configuration and should I perhaps change the batteries to a model with protection build into it (for added protection)?

 

[sailorman]

I'm not an electronic whiz, but shouldn't a VV with 7.4V be using a different circuit than the boost circuit that is in the Twist? Isn't the Twist a 3.7V battery with circuitry designed to boost 3.7V to 4.8V? Seems to me that it would be better if the batteries were wired in parallel, unless you are trying to make it function from 3 to 7.4 volts. If not, I would think it would be best to match the original battery voltage, since that's what the electronics are designed around. I'd definitely use protected batteries anyway. But what do I know?

Is it working in the same voltage range of the Twist? If it is, what's the advantage of 7.4 volts?