I also wondered whether my small 1/2 inch copper pipes may have contributed to lower current supply. I subsequently went out and purchased 1 1/4 inch diameter and 6 inch long pipes at my local hardware store. The current delivered by my zapper only increased by a small amount to 0.5 milliamps peak and 0.25 milliamps average. Thus, increasing surface area had little impact on current throughput.
No, my VOM does not have high resistance and is not limiting current. It is a Fluke, an expensive VOM. Also, I can measure my body's resistance and it is on the order of 10 kohms, about 10 times higher than what you assume for body resistance when you are making your calculations. This explains why the current being passed through my body is what it is.
This also suggests that you should not claim that your zapper is delivering 9 milliamps, or whatever you are claiming. If I were to use your zapper, I would not be getting anywhere close to what you are claiming. Instead, you could simply state that your zapper is more powerful than designs based on the Hulda Clark design - that would seem to be a fair statement based on what you described for your zapper.
I have been using a frequency generator to experiment with. I find that when I increase the voltage above 10 volts, I feel like I am getting "zapped!" (particularly at lower freqencies such as 2500 hz) While voltages above 10 volts may be tolerable, for me they start to become uncomfortable. I only do that sort of experiments with my legs to avoid the current/voltages from passing through my heart.
I also have been doing some literature research. What I have found is that if you are trying to use microcurrent for a theraputic effect (reduce pain, overcome injury), then 0.5 milliamps seems to be the sweetspot. At this current level, some studies show that both ATP and protein synthesis in cells are at the highest level. However, it seems that the wave shape is different for those devices which are used to achieve a theraputic effect. Instead of a square wave, these devices use a ramped square wave. In a ramped square wave, there is an initial high voltage, which ramps downward to a lower voltage at the end of the positive voltage. However, instead of a zero voltage period, there is also a negative voltage ramped square wave. Interesting stuff.... more later....