Depends what you're fixing. For T-grain film, two baths with 150 g/L and the second bath switched to first (and new second, old first discarded) will come close to that capacity. For other films and conventional silver gelatin prints, you ought to be able to get close to twice that (especially with two baths) -- the problem with prints, though, is that it's hard to see when the fixer is slowing down and getting exhausts, and tests for fixer exhaustion aren't very accurate (they test for dissolved silver, but can't detect iodide buildup from designer-grain films).

I've seen figures as low as 60 g/L for one-shot, minimum liquid processing of prints -- used in single-tray handling of large prints in a small darkroom, the idea is you put the print in an empty tray, pour in the developer, agitation, pour out developer and add stop bath if used, pour out and pour in fixer, discarding each chemical after a single use and using just enough to cover the print. Commercial non-rapid fixers are mostly similar strength to what you got from the Reilly monograph, though with sodium sulfite added for multi-session life (typically between 20 and 60 g/L sulfite).