Paul,
Those of us who are experimenting with the shots all have the same story.
First, if it were me, I would keep some notes on what each dose accomplished and for how long until you get the magic number. There have been several threads here in the last few weeks about reactions, and more than one about late night trips to the ER.
My minimal Trimix experience started at .10, that did something, but not much, .11 was better, and .13 that held up for 4 hours solid - I was headed out to the ER before it backed off. So finding the right dose is a challenge. And from what my uro says, the side and spot you pick for the shot can make a big difference as well. He is of the very small increases, and ask him first school of thought.
A recent book I read also makes the argument that the first shots break up internal plaque on the tissue that has accumulated from lack of use. His idea is that the same dose can have increasingly good effect as the pipes get cleaned out.
My uro, and a few books I've read, are very against mixing the meds. First, you lose track of which one is actually working, and second, you increase the risk of that trip to the ER.
I expect a few of the guys will chime in shortly.