What is the best solution to cover half hole? 
It’s down to individual preference Stef.
On small whistles I tend to slightly curl my finger slightly more so I cover the half of the hole nearest to the hand. Some people extend their finger slightly and cover the half of the hole away from the palm. I think this sounds more muffled.
On larger whistles like a low D, I tend to slide my finger down the body so I’m covering the half of the hole to the bottom end, because I’m using pipers grip and this is easier with my hands.
Thanks Martin, I will try your method, 
G# = keep yer ring finger straight, and place at 45 degrees over the hole.
This works for all size (D 
) whistles and at any speed.
I got the idea from Ivan Goff a few years ago. Until then I used to use finger tips, but the straight finger is much better - in my opinion of course
HTH
i’m sure any pro will use this method, but he or she will also transpose as much as he can, because it’s not so easy to blow a correct half hole. except for C natural (0++000)
(martin’s a jack of all trades 
)
Be aware that in some cases, to get the right pitch, you only need to lift your finger slightly… So that you’re covering 3/4 of the hole instead of half of it. Experiment with an autotuner to find the right amount of coverage for your whistle.
G# XXOXXX bottom octave
XXOXOO second octave
works well for me.
brian