Nice box that should greatly help prevent one of the possible causes for a fire, chafing and dings caused by dropping or crashing the bike, or a pebble getting into the enclosure, or a bolt head rubbing a hole.
And looks like it will provide good compression, as the packs begin their normal swelling with age. Well done.
But I don't see how it will keep the garage from burning down, if the bike is parked less than 3 feet from anything flammable, or the roof is within the usual 8 feet.
Isn't carbon and the resin used a flammable material? Sure, maybe a lot less flammable than shit like coroplast, and it should direct the flames out the top pretty good at least in the beginning. So why is that safer on your bike? What prevents the fireball from igniting roof framing or just the paint if your garage is sheetrocked and painted. Lots of garages are bare framing, is yours?
It could help to put a lot of sheet tin on the ceiling where you park. Or some cement based siding. I am not getting how you have any protection from a fireball if the pack should go off.
I'm sure you already do the real fire protection stuff, weeded out any bogus packs before you boxed them, stop before you wreck them with overdischarge, balance when needed, etc.
Since I remove my packs to charge, I notice anything wrong, like a cell got all hot. Add a temp sensor so you won't charge a pack that had an unexpected problem. Just check for heat before you plug in.
My own garage has a more or less valuable car parked too close to the bikes, too much junk that can burn around, and a painted sheetrock ceiling. That paint will burn way too good, and spread the fire if I charged in there and had a problem.
Of course, regular cars burn all the time too. At least my garage does have a fire block wall between it and the house attic. But the house was designed with few exits that aren't right by the garage. First week in the house, I was sawing a hole for another exit, on the far side of the house from the garage.