What's the current head tube angle?

What's the current bottom bracket height?

What's the current frame size and wheelbase?

Without knowing this, I'd recommend 80mm as well. The extra 10mm of axle to crown height difference between my 75mm Jett XC and my 80mm Duke XC was noticeable in its effect on handling.

If I went from 75mm to 100mm on my Backwoods (old school geometry), it would get hyper stable and downhilling would be a blast but I could no longer negotiate tight switchbacks.

My Zaskar's head tube is about a degree steeper (newer school geometry) and the effect would be similar but tight switchbacks wouldn't present as much of a problem.