The variances from sled to sled is not a wire size or grounding issue. I think the variances lie within the electrically components being used in the system, ie. ECU, coils, starter motor and even the battery. Ever component is most likely within an acceptable tolerance but when assembled together the tolerance variations cause a boarder line acceptable condition in the circuit so from sled to sled there's going to be slight variations in these electrical systems. I believe the Cat ECU design is the direct cause of the start problem. It's circuitry wasn't designed to compensate for the start cycle drop in voltage on these Yamaha 4-stroke engines and with slight variations in the electrical system some are more prone to start issues . I agree that the wire size used from the battery to the ignition could have been bigger but it is sized properly for the distance and load it carries but if you still think it's an issue just parallel another wire from the battery to the ignition fuse to decrease the overall wire resistance.
There are a lot of assumptions on why the problem exists but from an engineering standpoint I haven't heard anything that would make me believe anything different. I think if it was a simple grounding issue or improperly sized wire Yamaha would have addressed that. Those fixes are on a dealer's level which has to be cheaper than a team of engineers trying to correct an ECU problem.
RTX, I believe the 2016 flash update, unlike the 15 flash will protect against kickback because it might be detecting the low voltage condition and shutting down the ECU to reduce the chance of internal failure. This is an assumptions but if the ECU struggles with processing during a start cycle it makes sense to abort a start attempt. The 2016 flash, if this is in fact what's happening may be the only protection you are going to get to insure it won't kick back. It's up to you on how to proceed.
