I´m currently playing a Copealnd low D and I´m thinking on order a Overton big hole.
Could someone tell me what to expect in difference?
I know there´s a difference in air and back pressure and I have some feeling to the differences in timbre, but still wants your inputs fellow whistlers 
How is the balance between the two octaves on the Overton? Sometimes I wish that my Copeland had a little softer 2nd register (or a little hihger volume in the 1st).
/Pan
The Overton is slightly louder in
the lower register than is the
Copeland, so the balance may
be more to your liking. In general
it is the louder of the two
whistles, but not by much. There
is more back pressure in the
second octave than one has
with the Copeland (which has
a very accessible second octave),
but it isn’t excessive.
The Overton tone has been described
by the Undisputed as ‘the cosmic
drainpipe,’ which is apt, I think.
I much prefer the Copeland tone,
but that’s me–most people like
Overtons better than I do.
The Overton low D is less breath sensitive
than is the Copeland, and it’s easier
to control the pitch.
Of course, the Overton is lighter.