That is a good looking mount. If you put the ventilated ply plate on the OUTBOARD side you can install the pack from the other side & centrifugal force in flight will help hold the pack in the battery pocket.
My personal bias is to try to make the inside of the plane look as good as possible, because that's the part that I have to look at when I'm flying it. So I generally try to put all the ugly stuff (motor, tank, linkage, etc.) on the outside. It may not be best by any other measure, but it does keep the inside uncluttered.
On the other hand, we had a contestant (I can't remember the
name) have a battery come adrift during a flight at the Fall Follies -- had he put it outboard that may not have happened.
Side note to Walter if he's watching NICE JOB with the mount!
Yea verily.