I think I have a solution to this problem. Completely remove the box all the way back to the CG mark. Build a new stronger box that slides in where the original box goes and bolt it in place to new plywood sides, and notch where the original floor sits.  I can make two boxes, one for glow, which includes the tank, and one for electric that has the battery tray.  The Glow one would include a plate that covers the bulkhead that the cowl attaches to and have a few bolts lock it all in place, so rotational torque from the motor is handled as well as strengthening the fuse up to the CG point.   I can then fuel proof the box and seal the tank inside it.  This should make it cleaner and less likely to look like a hack job. <div>
</div><div>I can leave the original box sides in, there is at least a 1/2" clearance with the current battery so I can make the box out of 1/4" ply.  Some spruce corner blocks epoxied in at the front should help strengthen it up too. </div>