The UA revised ranger's Animal Companion feature for the Beast Conclave says that any beast of roughly CR 1/4 can be a companion (size Medium or below, 15 or less HP, and deals 8 damage or less a turn).
The giant owl is large with 19 HP and deals 8 damage.
This is comparable to the ape or black bear in HP and Damage.
The giant owl has a fly speed of 60 feet. This is the main issue I see, as neither the original or UA ranger companion list had beasts with a fly speed, making me think this is a powerful feature.
As an ordinary owl is CR 0, it hardly seems viable for a companion.
If the giant owl's size were reduced to Medium, it fits with the guidelines and is comparable to default companions.
Is it reasonable to allow a giant owl as a UA revised ranger's animal companion, or will it be over powered?