Slapi, I'm looking at putting the battery under the hump of my 350F build. An AGM battery model number XTZ7S measures 4.4375" wide x 2.75" deep x 4.125 " high, or a similar Yuasa should work. They are both sealed and can be laid on thier sides. What tail did you use (Glass from the past)? Is there any room underneath? Anxious to mock mine up now.