Just had to google the route, looks like you'd be better off on 28mm slicks at about 80psi................
And rolling on, if you've been on Fire XCs for that long, its probably time to move onto something designed within the last 20 years. I used to use them for everything (except racing) until about 5 years ago.
Have moved onto Racing Ralph/Nobby Nic combos, they seem to be the modern equivalent. Comparing back to back, they do everything better.
And if you are running that sort of pressure, i'm not surprised you still think Fires cut it!