Sorry that I wrote in decimal units, being a Forum with a majority of US members. As a general idea, 3mm equal about 1/8 of an inch.
WOW, half an inch out! I have tried to play with the HJ so far out (and also .75") to tune with recordings of Haendel sonatas on baroque flute, but the general tuning was so difficult I gave up (and got a recording on a modern flute...)
I have just tried settting the Korg tuner to 440 and I can play in tune without much problem with just 1/8" HJ out. But I tested only A1, A2 and A3. This last is +20.
So many other ideas in a short time!, OK:
No, I use plugs on every key except middle finger LH. Possibly no leaks at fingerprints on that single finger. I have rather soft finger skin as my job has been mainly office and computer for many years.
Cork fit, well, I want to suppose the technician that repaired the tenon bent checked this, but I cannot be sure. Anyway I don't feel like disassembling the HJ again, I still have to fully recover from the shock I had with the HJ fall.
As for lowering the small C key it was just a test to see whether this could improve the Eb2 quality. Nd it did not.
At this moment I feel confident that I will manage the Eb problem with enough training (long notes and the like). I am working the Taffanel scales (specially the expressive scales of exercise 4, which I like most). This must help with my sound quality, including Eb2, I hope.
I have decided to increase my dedication to the technique part and I am trying to get two extra, one hour lessons per month, just to work out those aspects. (yes, I am in a period of flute enthusiasm).
I also dropped my sing lessons for the moment and the English literature group, because I was having too much stress and was too short of time (and money) with so many interesting but demanding activities.
I plan to concentrate on the flute learning and will try to keep active membership in the choir, very demanding too but something I love too much to leave.
Although I feel enthusiastic concerning the flute, I also have the feeling that I have not advanced enough in these years (I am on my 6th year of lessons). And I plan to catch up quickly. My teacher is very supportive and understands my yearning to advance, even skipping sometimes one important aspect or two.
Sorry, seems I am too much talkative today, my apologies...