Andy Cutler says you need to dose the combo according to the chelator that has the shortest half-life (the one that the body does not retain so long).
Remember the goal in his protocol is to keep relatively stable levels of chelator in the body. We want to increase the odds that when a molecule of chelator drops a heavy metal--HM--there will be another molecule of chelator available to grab onto the HM. We don't want the kicked up HM going from a part of the body that is not very vulnerable to HMs to a part of the body that is very vulnerable to them.--brain, liver, thyroid, adrenals, etc.
I make my own custom capsule similar to what you deescribe. This enables me to choose the dose for that round. If I have nothing pressing to do that weekend I might choose a higher dose. If I have obligations I'll choose a low dose that produces almost no side effects.
I bet the dose of the premade chelator combo will be too high for Cutler's frequent dose protocol. People new to his protocol often are taking less than 25mg doses.
For a mercury problem, people often never take more than 25mg DMSA.
Remember, people with immune system weakness may not tolerate much DMSA or may only tolerate it one round every month or two. That actually might be adequate if you don't have much of a lead problem.
Results of DMSA Treatment Study, James Adams,et al
Conclusions - benefits
•DMSA greatly increases excretion of lead, and some increase in excretion of tin, mercury,thallium.
•1 round of DMSA dramatically normalized glutathione levels for at least 1-2 months, and helped normalize platelet levels (marker of inflammation) for at least 4 months
•Severity of Autism Scale. Significant improvement in both groups
DMPS is typically reported to be preferred over DMSA by most detox members I've come across. The effect is "smoother" and side effects typically less.
I'm not discouraging the use of DMSA. I've almost exclusively used it with good results for my lead and cadmium problem.