2010 Prius S6 Whispbar rack system bar spread?

I have a 2010 Prius and I just bought a S6 Whispbar rack with K458 fit kit and am wondering about the bar spread distance. According to the manual, the exact bar spread should be 23.6" and each bar must be attached at specific points on either side of the b pillar. My end goal is to get a cargo box and eventually a bike rack.

I also called Yakama to get their 2 cents and they definitely recommended that I adhere to those measurements and contact points, they also added that most of their boxes require a minimum 24" spread, which is within tolerance of my measurements.They also added that their cargo mounting brackets only need 90% contact to the bar to ensure a solid hold.

Despite this, this spread distance seems narrow and the contact locations seem impractical to me, so does anyone have my same set up and can offer any insight? Has anyone had needed to change the contact points beyond the manufacturer specs without any issue, perhaps a lot of other cargo boxes and bikes racks on the market require a wider distance for stability? Yakama also added that deviating from the manual's specs could result in a premature failure of the system.

I've ran across a few pics on this forum and most of the bars seem to deviate Whispbar factory recommendations, any insight on this matter would be greatly appreciated.

Thank you.