Any of you have any experience with the Butternut HF-9V with TBR-160S
160-meter add-on, when mounted as a ground plane with the base elevated
to, say, 20 or 30 feet?

I'm wondering how that will work with four ground plane radials as
contrasted with ground-mounting and an extensive buried radial system.

I have the ideal place to mount one, about 25 feet in elevation at the
base, and can string two radials for 160, three radials for 80, and four
radials for 40, tilted down a little (but not the 35 degrees of downward
tilt that I read somewhere is the ideal downward tilt for a ground plane
to raise the feedpoint impedance to 50 ohms).

I'm hoping that those radials will also be enough for operation on 20
meters... it would be difficult (but not impossible) to also string four
more radials for 20 meters.

Ground mounting this antenna with an extensive buried radial system would
be very difficult (but not quite impossible if it would REALLY make the
difference).

What are my chances for good success working DX with this setup and about
70 watts of power?

Would it be worth the extra effort to try to get the base of the antenna
up to 40 feet rather than 25 feet?

Thanks...