@ Andrew,
Thanks for sharing. We will be checking out the Bivo. Their cap and (gravity) flow rate looks ideal (ex-NASA developed!). Will be on the lookout for their insulated model, hopefully soon.
We continue to use Hydroflask models, but the flow rate out of their specific mouthpiece is just so-so. Plus, cleaning the inside of their cap can be concerning, lots of nooks and crannies.
@ Miles: we too use King Cages (with above stainless steel Hydroflasks). We've found the King Cage 'Iris' model cage to hold a naked stainless container a little better vs. King's (we've used both models of King Cages). The amount of friction between the two King Cages is clearly evident. Granted, we were not using this specific combo off-road though.
While off-road we used the large wide-mouth Hydroflask (40 ounce - 1.18 liter) insulated container with a BBB XL Fueltank cage + Voile strap. This combo was extremely secure in all kinds of rough terrain (it never ejected off the bike). It obviously removes the possibility and ease of drinking while riding a bike though. It was simply a way to carry a decent amount of water securely while cyclotouring/bikepacking.
Best regards,
Jeff
Claremont, CA