I think the "2003 update" of the circuit is even decreasing the effectiveness with reducing the delta of the front from 8.9 down to 8.75 volts (since the new schematic targets the lowest voltage to be around 0.25V compared with 0.1V in the old circuit). From schematic point of view it is impossible to have "negative" pikes even with the old circuit, no matter with or without load it is measured.
It is another story the believe, that the negative voltage is maintaining the parasites existence. I think it is totally wrong. You can check that practically EVERY electromedicine device (except Zapper) is using bi-polar (or even mostly negative) impulses - TENS, EMS, Scenar, Eledia, Denas, all the Voll-methodology instruments, etc. Does this mean that people using such devices should become more and more sick...