Yes manybags, it will be possible for some to take huge quantities. I don't believe that I said it wasn't possible.
What I did say was that for many who boast of their ability to take huge quantities it will be a boast which they cannot prove here - in other words this thread and others on the topic can turn into a competition, which is scarcely useful to the membership.
Of more concern however, as in the last line of my post, is that others may unwisely try to emulate or even exceed those stated achievements. There is danger there, in that in doing so they will throw caution to the wind and transfer faecal matter into the stomach and the upper digestive tract - hardly to be recommended!
Because Sears Roebuck (once) sold 3 qt or more equipment proves nothing - they didn't say that it was OK to make it 6 qts by refilling it, did they? Nor were the women who say that their nurses administered larger quantities necessarily correct - there is only their word for it.
It is, as you say, highly likely that a larger quantity of water will remove more faecal matter but the size/weight of an adult persons body is little to do with it. What is at issue is the size of a persons brain, the caution they exercise using that brain (and you may well have used caution) and the reason they are doing an enema at all. If it's simply to take part in a competition against an unknown competitor, whose veracity might be questionable, then it is most certainly undesirable.
Anything stated in this Forum, even by supposed professionals, should be viewed with caution and not with imitation.