I just answered a Tenergy Battery question at AirsoftSociety.com from ncbairsoftteam, and I thought it was worth sharing.
Question: Is a 8.4v 1100 mAh Tenergy battery any good? I already have the 9.6v 1500 mAh, this would just be a back up.
My Thoughts: The batteries made by Tenergy are great batteries. In your case you will notice the rate of fire compared to your 9.6V will be slower, but that is because you reduced voltage. The battery will probably seem like it is lasting about the same length of time even though it is 400mAh less capacity. This is due to the drop in voltage as well.