7100 is max. We run a 17T with 65-73T axle sprockets. So around a 4:1 ratio, plus or minus 0.3 ish.
And from what we’ve experienced and what I’ve read, you ideally want to gear for hitting the rev-limiter ~2/3 down the straight(s) before braking. So hitting the rev limiter is the best way to set your gearing. Kieran hates when it happens, but it helps keep the gearing OK for digging out of the tight corners elsewhere.