I have always found Cathcart's discovery of the Bowel Tolerance method of dosage determination to be an absolutely "magical" thing, because it allows a person to self-dose, i.e. with no need of a health practitioner and/or body fluid check whatsoever. And not only "self-dose," but even pro-actively "derail" any and all pending health maladies, i.e. at least in theory. However, at least initially, depending upon a person's overall GI tract health, they may not be able to [orally] ingest, i.e. absorb, an optimal amount of ascorbate [for whatever current health malady they are facing]. When that is the case, IV/C, and now [apparently] liposomal ascorbate, can be used [very effectively], because they cause no Bowel Tolerance reaction, i.e. thereby allowing a theoretically unlimited amount of ascorbate intake [and, at least in the case of IV/C, "absorption"]. I do not know if anyone has ever tried to ingest 20 to 40+ grams of liposomal ascorbate all at once, i.e. to see if there was/is a Bowel Tolerance reaction [or some other useful indicator(s) of "saturation"].
But, yes, you are correct, Dec, i.e. that always leaves a person "guessing" as to how much ascorbate is "optimal" at any particular moment! Without Bowel Tolerance, one is left with checking fluid levels, i.e. of ascorbate [and I am not sure if that would tell a person all they wanted to know], and/or symptom amelioration [not as precise, in the immediate/short run, but effective ultimately].
The only [practical] way to "untangle" it, Dec, as far as I can see, is to ingest a Bowel Tolerance dose of ascorbic acid every day of your life, i.e. and let Nature takes its course!
Just my viewpoint and "two cents worth," Dec, and I hope it helps [with your challenge of "untangling"].
JFYI, I have ingested a Bowel Tolerance dose of ascorbic acid [via one gram tablets], in HEALTH, not illness [of which I have had virtually none], basically every day since 1994, amounting to [currently], on average, 75+ grams [daily], in 10 to 15 divided doses.