Hi Jim
Perhaps we should keep in touch as I am building the same boat and only about 3/4 weeks away from the maiden launch, my set is as follows.
2x Graupner 600 Eco Motors
2×30 amp M troniks speed controllers
2x 8.4 volt 4300 nimah batteries made up from sub C cells
1x Action Mixer Unit
I have spoken to several people over this and taken a lot of advice the only problem I see is the size of the batteries as most folk told me to use 3200 nimah but using the 4300nimas i am hoping for a longer run time. I may not be able to use full throttle owing to the additional power but the test runs will hopefully give me the answer. I have also been told that the boaut does no reverse very well.
However hope we can keep in touch and swop our ideas
Cheers for now
Rodders