This is what the Osmo mobile looks like with my iPhone 7 plus attached and the arm fully extended.
I've read about extending the arm beyond the friction point, unscrewing the adjustment knob fully, pulling it all the way to a complete stop (goes "clack" at the end stop when pulling it)
But still not balanced. It's got a .3 mm tempered glass screen protecter attached, but no case.
I have my iphone 7 plus with the 3.5mm jack connected to Rode mic i have to extend the phone off a little and then counter balance the offset with a bag of coins. ...
I am hoping the DJI Osmo 2 will be iphone 7Plus friendly.
the glass screen protector should have no effect on the balancing of the left and right.
I would definitely contact customer service, Mine balances very well (although no glass protector) and sometimes forget that i actually have the unit turned off.