Answers in bold
First things first--Happy Easter!
Happy Ēosturmōnaž to you, Dr Mark
What is the measuring device that was used to detect the two pitches. The problem I had using a regular Korg type tuner it was hard for the tuner to detect the air sound.
Ear. It serves me well.
Never the less, we now know quantitatively that the Bb Wild Thing with Denis Wick 2W has matched resonances at 230Hz. ~20 cent below concert Bb.
Strictly speaking, we know that if I pull my main tuning slide out 35 mm, my low C is a tad flat
That sounds like a lot but I've got to ask:
At that setting:
Did the horn vibrate more in the hands?
Did it play easier?
Was the sound brighter?
Not noticeably. In fact, I recall no horn I ever played (even when I was quite good), showing a significant change in playing characteristic for a reasonable pull on the tuning slide. It's actually quite interesting to consider the impact of such a thing. You could find yourself in the position of claiming "Of course I sound rubbish, the oboe's 20 cents sharp". Actually, if we did come across an instrument with a performance that was significantly sensitive to tuning slide position, wouldn't we discard it as a poor design? Just a thought.