I’ve done just that - not an oak but a tea-tree (Melaleuca Alternifolia). The combination of moving the setup about 40m uphill and into the tree gave me an extra 8 metres in height amsl and an unobstructed view out to sea to the south. This significantly improved the range at which I first pickup the few aircraft in that direction.
I think another factor affecting range that’s worth mentioning is atmospherics. I’ve only had the antenna relocated for a week, but the maximum range seen in the last 24 hours has been exceptional relative to previous six days:
No changes to my setup (or the number of distant aircraft as far as I can tell). The thing that has surprised me has been the altitudes of some of the most distant aircraft:
The southern-most track starts at 10775 feet, around 300 NM from my location.
(Note that the 40,000ft heywhatsthatcom-range-outline is from my old location, but I don’t think it will change much.)