Don't change the oil weight ! The hydraulics are set up for a certain viscosity, besides, hydraulics are not your issue, just spring rate.
Increase the oil level for more air springing effect towards the end of travel.
I'd be very careful going past 0.95 kg/mm regardless of what the charts and online calculators will for sure otherwise say, likely guiding you beyond 1.0 kg/mm.
(Doubly so keeping in mind that online calculators are notorious for calling for too stiff fronts and too soft rears when it comes to 919s.)
The 919 is more rear wheel weight biased and has horrendous fork stiction.
If your riding is not heavily performance oriented, and you are riding with a stock rear shock, I'd suggest 0.95s with as much as 20 mm of installed preload, 125 mm oil level height, and try that out first.
You want compliance in the front end, and you'll lose it with excessively stiff springs, and all of this gets worse if you ride on rougher roads.
Suggest you poll some of the guys here you are big boys and have done some spring rate changes at the front.