Ok. Goto
http://forums.wbta.us/ and register. I'll have your forum up and ready in no time. You have the choice of allowing replies or not.
As long as the cartridge is meant to be used immersed, that's good. JD had an excellent idea of using one specifically made for that. Otherwise I'd tend to go with some kind of block, be it copper or otherwise (stainless steel?!?).
The clampmeter only works for AC; it's useless in DC (since it measures fluctuations, and DC has none).