I have 3 holes, maybe 1 - 1 1/2" in diameter in the lower tank support. It was a real pickle to get the blind nuts in for the landing gear. I have a set of curved forceps that I could finally position the blind nuts with to get them in there. No way a battery would fit, unless I cut that section out, and fit something else in there. I had thought of doing just that because I wanted to make it a taildragger.

The exhaust deflector "flopped" around the mounting as it's axis, not rotating on the exhaust flange, but just due to it's flexibility, like a hose under pressure. I think it was a Hobbico, with the support web to the inside of the bend. To keep the exhaust off the majority of the plane, it would have to be about 5 - 6" long and rigid, to keep it from flexing too much. That was why I thought that you may be able to make what I wanted to do out of some thin tubing, and get it down just below the belly.