Just finished "tightening" the battery position adjuster. I paid close attention to the plastic platform surrounding the battery latch, and up/down position of the battery. Tightening the adjuster actually compresses a spring that presses the plastic platform upward. Doing so lowers the platform into the bottom bracket area, and also eliminates all upward compression from the platform. Pressing on the platform reveals it is bottomed out when the 5 mm hex adjuster is tightened completely (righty tighty). The battery also sits much lower, with noticeable gap at the top of the battery and frame.
So I reversed my thinking. Loosening the hex adjuster will cause the spring to push the battery higher. The battery now fits more snugly in the frame and I feel more resistance from the plastic platform as the bottom of the battery (with Teflon tape) slides in and presses the platform down against the spring.
My conclusion is that loosening the hex adjuster is the way to snugging the battery in the frame. A bit counterintuitive.
It helps to have a stand to make these adjustments to the hex - but it's a bit of a strenuous lift and hold challenge while mounting it on the stand, even with battery removed.
Jon