I use 6mm bullets on motor and battery. The main reason is that they are easy to solder. I can't solder a dean's plug to save my life. I like the traxxas too, but I just find soldering the bullets to be a lot easier.

I like the idea about a plastic adapter for safety to keep the bullets from touching. I blew a lipo pack though on accident (remember that JHautz!) not paying attention. I since have switched to male/female set up so I can't make that mistake again. IT does bother me though with the exposed connector. For now I just wrap in electrical tape as a safety precaution.