Bear can … existing [Y] strap .. not long enough
A number of videos out there showing BV’s being loaded into the Pa’lante V2 37L (larger size packs), .. and even the GG Kumo 36L. One common denominator is a 30°F UL quilt at the bottom and the BV atop that with soft gear layered around.
Jupiterhikes stored one vertically inside a Pa’lante V2 on his PCT hike last yr and has a short YouTube video about it (link not pasting for me). It’s dated 6 Mar 2023 as of this post. Note he’s a pretty spartan hiker with knit a Zpacks flat tarp, no sleep clothes, etc.. Feel a stuff sack of clothes could be strapped below the “Y” strap if need be.
The 450 and 500 have the same circumference but the latter will require more room obviously.
I’ve seen strapping bear cans on top, but they seem slippery.