Robert Forward (the author of Timemaster) was a physicist and I would do a check of his anatomy related topics before getting into one... but I would be confident of his math.
He wasn't unfamiliar with the technology being used.
https://en.wikipedia.org/wiki/Robert_L._Forward
> He then went to work at the research labs of Hughes Aircraft, where he continued his research on gravity measurement and received 18 patents. He took early retirement in 1987, to focus on his fiction writing and consulting for such clients as NASA and the U.S. Air Force. In 1994, he co-founded the company Tethers Unlimited, Inc. with Robert P. Hoyt, where he served as chief scientist and chairman until 2002.
https://en.wikipedia.org/wiki/Tethers_Unlimited,_Inc.
> Founded in 1994 by Robert P. Hoyt and Robert L. Forward, Tethers Unlimited began developing products based on space tether technologies, including concepts for removal of space debris and momentum exchange tethers for launching payloads into higher orbits. TUI has since broadened its suite of technologies to include power, propulsion, actuation, and communications systems for small satellites, robotic technologies for on-orbit fabrication and assembly, optical fiber winding and deployment, software defined radio communications, and 3D printed radiation shielding.
...
And so, on his word, I'd suspect that it would not be unreasonable to do a fluid breathing 30g ... given the right fluid breathing setup. The rotovator setups are looking at significant fractions of a day for earth capture to space release (6 or 12 hours). I don't think there would be human significant jerk, snap, crackle, and pops either. Though again, I'd be curious to see that acceleration profile (not that I'd ever be doing it myself).