If it's of any help, in my experience using RAM I haven't had any issues. My fish finder, camera, evolve motor control, RAM fishing rod tube, and soon action cam are mounted using them. I've accidentally kicked the fish finder when trying to exit the yak and it did not affect the position of the RAM mount, though fortunately the FF base holder tilted. Very versatile when it comes to positioning devices especially things with screens that don't display well in sunlight.
For the battery I got the Hobie big fish finder kit and taped velcro to the bottom of the battery and the hull of the kayak.. placed it in the battery foam to counter potential roll in rough waters. In practice it's definitely gonna stay put on the water.. it takes a firm tug to get the velcro to unhook. The stock PA tackle box cage fits and operated perfectly though I don't use it. I like to store my lunch bag, first aid kit, dry towel, etc in this spot.