Outback PSX-240 and loads balancing

[SolarMusher]

Hi Folks,
Finally, I've just finished to rebuild/renew my old system with 2x VFX3648 (7 years old + new demo unit) using Outback serie/parallel stacking + PSX-240 transformer and was wondering if someone knows how it really balances loads when above 12Aac? On the mate (old oval display), I've seen the master at 10A (P01) when the slave (P02) was around 6A.  In the PSX manual I saw a diagram which was showing a nice balancing between both legs but real life seems a bit different. Does it need bigger loads to get a better balancing?
Any ideas from Outback users?
A+
Erik