Battery mounting with Luna & Grin?

Hey all, pretty new here but have been around DIY lithium batteries for awhile. Trying to figure out a good solution for a removable battery mount. I have a rectangular 10S5P pack that I would like to be able to take off to charge/swap with a fresh battery. I do still use my bottle cage, and ideally would mount the battery under my top tube. A triangle bag isn’t quite the right size and loses the bottle mount, so I was thinking of some combination of the Grin Triple Bob and Luna Wolf Magnet mount, and then including steel backing plate in my pack. Thoughts on the magnet holding on a bumpy ride, of combining it with the Bob, or generally hanging battery from top tube?

Thanks!

This might be helpful
https://endless-sphere.com/forums/viewtopic.php?t=100132