We run 19/43 here in sweden-sold 100 of kits.
Works with stock chain -Top speed is the same about 86mph/141km.
But trackspeed is greatly improved.
But we dont have xtreme altitudes like you
If i would be at higher alts. 19/45 works better but
Is a little overkill at. 1000-3000 were we ride.
Ihope Polaris reads this and use a 2.33ish ratio for the new belt
Drive....