If you lay out all the best Low Dās side by side youāll see that all of them have the toneholes pretty much in the same place⦠thereās a reason for that! All of the best Low Ds represent the best compromise between the laws of acoustics and human anatomy. (The exceptions of course are conical-bore Low Ds which have the lower-hand spacing compressed much like a conical-bored flute has.)
On an ordinary Burke Low D, Low E is already weaker than its neighbors Bottom D and Low F#. Itās because the E hole is, acoustically speaking, too far up the tube, which is why itās smaller than the F# hole. Ideally the E hole would be halfway between the F# hole and the open end, and just the same size as the F# hole. (Just look at the size and placement of the toneholes on a Boehm flute, which has all the holes the ideal size and place.)
Low D whistle makers do this because of human anatomy. They make the E hole higher and smaller so that with the pipersā grip the instrument can be comfortably played.
Iām guessing that the āEZā (boy what a Red Flag that is) has the E hole moved up the tube even higher, even further away from its acoustically ideal position, making it even weaker. You canāt move the toneholes without paying the price.
My advice would be to either 1) master the pipersā grip so that you can play any good Low D comfortably or 2) switch to a conical-bore Low D, which will have the lower-hand holes closer together.
(I know about the Burke Pro Viper Low D because I played one as my primary instrument for a few years, before switching to the MK. One of the great things about the MK is that, unlike most Low Ds, the Low E is the same power/strength as its neighbors. Part of this, though, is due to the fact that the MKās Bottom D isnāt as powerful as the Burkeās.)
Every Low D Iāve tried which has had the E hole moved even further up the tube than usual has had an unacceptably weak Low E. I had, at one time, a Low D which was even more odd: the maker, in an attempt to make the arm reach for the lower hand shorter (maybe people with short arms had asked for such) had moved all three lower-hand toneholes further up the tube. G emitted from a small hole right up next to the A hole and E was a tiny hole situated about where the F# hole normally is. This whistle was awful.