Yes, there is a ton, er, many a cubic foot of unused space! For now I would like to be able to toss it out of the car if it burst into flames, but the longer i play with it the safer it seems. I have not decided if I want to put some of them where the rex would have gone or put them all back further between the motor area an the rear bumper. I could spread them out and keep them all low, or if it is mainly for winter range extention, mayby rear most is the best for winter rear wheel traction. I was concerned that having the modules at different temperatures would cause the voltages to change but they remained the same with a 20f degree difference. I 8 modules I will be using are 27 lbs each so 162 pounds plus what I contain them in. 9kwh all together. Can anyone recommend a source of info on ISTA ? Can it help me tell my car I have more kwh than it previously knew about?