Well, I'm not proposing that it is critical to modify the front calipers. But...
Starting off theoretically speaking, Force = Pressure x Area. By maintaining pressure constant and increasing area, you would, therefore, increase your force applied to the rotor.
I couldn't say much, but my friend and I did trade bikes for a moment and went cruising through some canyon rodes. He rode a 2007 R1, and I had my R6S at the time.
If I have the urge to take it (the FZ8) on the track, which I did with my R6S, the 6-Pot brakes could make an improvement in braking force and feel. More surface area over the rotor can make for stronger braking force, even though Pads play a significant roll. 6-Pot, with Pads great for track use, (and of course some very sticky tires), would make a significant improvement.
According to the specifications, the FZ8 appears to be heavier than the R1 by approximately 30lbs. So, the use of 6-Pot can benefit here.
For daily use, there isn't any significant benefit other than brake feel. I felt the 07 R1 had better brake feel than my 07 R6S.
Other than this, the last point I could make is by an observation. We clearly see that the 454lb 2011 R1 has the 6-Pot caliper. How would the 4-Pot be any more efficient for the FZ8, when this bike weighs 30lbs more? This isn't even accounting for the weight of the rider.
But remember, it is not critical to modify the front calipers. But, if a person like myself visits the track every so often, there is a benefit to upgrading the forks for adjustable forks. And, since one would have the forks of the R1, why not use the brakes as well?
(Edit: Wow... I wrote a lot...lol. If anyone feels I am misunderstanding or incorrect about something, PLEASE call me out. I am always happy to get my facts straightened out.
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