Well I went ahead and bought a Pulse XT. My two A123 4s 2300 packs fit great. I just sanded the rear battery area former so they could side in and out easier. Once in they fit infront of the former. Now I have ordered the motor etc to finish the build. Then I get to see out the cg works out.
I hope the Power 46 runs on 4s A123 ok as it a little lower voltage than lipos.