Not too fast, with lots of turns. You don't want big drops. I usually do a nice curving drop, then come up, go back down a big, do a few big sweeping turns, drop a bit more, more turns, (trees nearby help excitement). The nausea is very hard to avoid, but 6.5 is not bad...they shouldn't be avoiding that. Heck, my best suspended has a nausea of 10.92, but the peeps love it. Excitement:7.09, Intensity: 8.81, 52MPH, 3261 feet long. They should be fine with nausea up to high 9s.
Sorry this doesn't help with the nausea, but suspendeds are inherently nauseating, and you should just shoot for high excitement while keeping the nausea and intensity below 10.
Jman