gjeffers, Something is wrong with your tank. Also my info was wrong on conversion. I should have stayed awake a little longer in class. But here is a link to convert cc to oz. www.onlineconversion.com/volumn.htm
At that website it says that one ounce is equal to 29.5735297 CC. I thought it was 28.4 CC. But anyway, using this formula 270/29.5735297 your stock tank would be 9.1 ounces. My H9 tank says 11 oz right on it. and it does hold a little bit more than the stock tank. Sounds like the H9 tank isn't 11 ounces for some reason. Send it to me and I will do a little add on.
Thanks.
Barry