Greetings,
Here are my notes on the Reviol low-D currently on tour.
In a nutshell, I think this is a great low-whistle !
Backpressure:
I rate the Reviol as middle-of-the pack on backpressure. I’ve played some with more, some with less. Ditto on air requirements.
Sound - voice:
The timbre of this whistle really shines ! It’s got a voice somewhere between the crystal-clarity of Susato and the gravel of an MK. I love it. Almost no rushing-of-air-sound. No latent white noise. It’s all harmonic power.
Sound - volume:
This whistle has plenty of power. The 1st octave is in the same league as my MK. The second octave is louder, but not screechy at all.
Toneholes:
The toneholes and their pattern are a little on the largish size. My hands are a little on the small side, so, this whistle took some effort. After a few days, I was finally starting to close the bottom holes reliably
Tuning slide:
Nice and firm. Very smooth. Wont move unless you move it.
Finish:
The matte finish gives plenty of traction for an easy grip.
Weight:
My kitchen scale reads 219g. More than some. Less than others. Light-ish for an all-metal whistle. I really like light whistles. They allow me to practice longer.
All in all:
This whistle has one of the loveliest voices I’ve played. Plus, it’s nice+light, which is good for practicing a lot. The holes and pattern are on the larger/wider end of my experience, but tractable with practice.
of course, Thanks to retired + Mr. Reviol for sending making the tour happen !
(For those keeping track: it arrived here 6/11 and I mailed it to the next on 6/14.)
Oh, BTW: I hereby nominate the packing for the “tour-packing-hall-of-fame”. No muss, no fuss, plenty of protection ! Plus: a clearly labeled “open this end” ! It’s the little things . . . just like a good fipple. 
trill