+1 for the B-RAD setup from Wolftooth, works great. (altho, the bag is now back under the saddle, as much as I don't like it there, because I've been doing TTs with this bike and it's too much trouble removing the whole setup, so I leave it on the saddle and then I only have to take the cage off).
My gravel bike has a mount under the downtube, perfect for a canister, wish every bike had that.
