The main thing to watch is motor temps when gearing up alone. I'm currently running the 2S2P 6.6v 4500 Green series pack in my Slash with a Castle Creations 5700 Mamba System geared at 18/86 and it's simply just plain fun to drive on my test track at home. Can clear my 8 ft. long table top jump with ease and throw dirt all over with the set-up. I actually prefer it to my 6500 7.4 volt Li-Po because that can be to much for the size of my track.
Jason