First, I'll reiterate what Gimlet said, as it needs repeating: Motorcycle lithium batteries are NOT the chemistry that can cause runaway fires!!! They are LifePo4, which are VERY stable. I throw that out there again, as this sort of mis-information causes a lot of issues with apartments, HOAs etc. Not just with motorcycle batteries, but e-bikes, boats, RVs and electric vehicles with LifePo4.
Second, I'd be concerned with the 4ah total capacity. Yeah, that's really 8ah lead acid equivalent, but it's still rather low (stock is 18ah). If it starts, that's great, but you've got next to zero reserve capacity for such a huge engine. If it doesn't start right away, I'd expect very few second tries.
I ALWASY put LifePo4 into all my bikes. I have over 10 years doing this in more than half a dozen bikes. I stick with Anti-Gravity, but I'm sure there are other good brands. At this point I haven't made the switch on my GT, only because there is not a Lithium that fits in our odd size battery compartment that has anywhere close to the stock capacity.
I'd love more feedback long-term as to how well this super small capacity battery does.