The aircraft only knows about the main battery and it's voltage and temp. What it sees is a battery that is draining curiously slowly but otherwise shrugs it off. The strain on the main battery is vastly reduced since the aux batteries are helping supply the needed current.
When the main (remember the internal sensors are inside the main DJI battery, not on the total parallel virtual battery) gets to a voltage level that sets the low voltage alarm off, the aircraft acts accordingly. It's as if the external batteries aren't there. So the % main battery level is what the aircraft sees for voltage meter, not the "virtual" battery made up of main + aux batteries.
Translation: the aux batteries only help, never hurt. Kinda like Googles mantra "do no evil". But that's another story.
No mod is made to the Inspire. No aircraft were harmed in the making of this thread

. It's just a battery mod. Pop in an unmodified battery any time and Frank Wang himself wouldn't know anything is different.
Handling wise, it's a bit more sedate but you don't want to strap a "big *** battery" under the Inspire. Just some helpers of the just right variety in terms of C, capacity and weight. I've spent upward of $1000 in lipos to find the sweet spot for an X3-toting rig and it's all documented in this thread. But I'll save you the 4 months and $1,000 bill to find out: it's 2 X 2700 ThunderPower 6S 25C's weighing in at 351g each. Best so far anyway, >30 min flight time to 10%. Still going to try a few more but that's a very nice combo.
Go too big and heavy (I've tried it all, including dual-TB48's, dual-TB47's, etc etc) and you just end up with a big fat heavy bird that flies like a drunken cow.
Hope that helps. Sorry for the delay responding, gotta keep my day job to pay for the experiments