I agree with your need to keep the camera on, but I think you are killing your batteries. If weight isn't an issue, apply some technology to the problem. Rig up a harness and wire a set of batteries in parallel to keep the load down on each. It will really help the lifetime of them. With my 300D and an IS lens I still get 400-500 shots out of a battery. You may be happy with only 50 shots, but I think you could easily be much happier and without the high load on your batteries.
This sounds like a job for a Quantum battery:
http://www.qtm.com/battery/digital_main.html
Sorry about the weight...
If weight really isn't an issue, go with gel cells in series and a regulator. We used to use a similiar trick on our ELPers (an interferometer for locating crashed airplanes)
When I was working at Collins Avionics (where I also spent a short stint in the Iowa Civil Air Patrol) we called them ELT's, for Emergency Locator-Transmitter. Spent quite a bit of ICAP air time chasing down ELT's that had gone off accidentally. Lithium batts were the norm for those.
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