7.2 lol, yes you are correct i would use just 2 speakers, probably lowthers, fed through directly heated single ended triodes and audionote transformers,
the other speakers are there to try and fool the ears your listening to a good 2ch ( none pidgeonholed recording )
it dont fool my ears one bit 
from what i can gather the sweep is done through rig control software like a cat system,
the minivna sweeps in the blink of an eye also does plots and no need to apply radio rf, i dont use plots on that either lol,
for me the lp-100 is a good vswr/wattmeter that shows min vswr point and where the antenna is x=0,
looping the amp remote through the alarm relay to protect against high vswr or overdriving the amp is a cool feature too,
maybe i will find a use for the plotting in the future i dont know
